Newbie here saying hello
 

Just wanted to say hi, my first day here. From N.E. Pa.
Brand new to this, and am trying my hand at hydroponic lettuce, as my wife has stage 3 kidney desease, and she eats a lot of it.
Probably have a lot of questions here for a long time, looking forward to advice from the you more knowledgeable folks.

Hello newhydro16,
Welcome and sorry to hear about your wife's stage 3 kidney disease, that must not be easy to go through. Feel free to ask all the questions about hydroponics that you need, and well be happy to help.

newbie
 

Thank you, shes doing ok, has a very strict diet, thus the lettuce.
I hope I can make this dwc work, hope I'm not in over my head, as the nutrients, ppm, and ph seems a bit overwhelming. Hope I don't drive you folks nuts while I try and get a sense of this. Have a happy Holiday.

Hello newhydro16,
Don't worry about it, it's very easy. Most people do so much research they over think everything, but it's not complicated at all. First don't worry about PPM/EC/TDS or buying a meter to measure it. You don't even need a meter to measure pH. You do need to measure pH, but all you need is pH drops. In fact not only are the pH drops much cheaper, but more accurate as well. Electric meters can give false readings, but pH drops never will.

As for measuring PPM/EC/TDS, you don't need to. It's very easy to know what your nutrient strength is by fallowing the nutrient manufactures mixing directions. Nutrient manufactures will give directions on how much to use per gallon of water. That amount is for full strength nutrients. From their you can use it full strength or easily dilute as needed. Seedlings don't need nutrients at all until they develop their first set of true leaves. Once they do the nutrients should only be mixed to between 10% and 25% strength. Then when they get a little bigger increase it to 25% to 50% strength. Then once thy start to really start growing increase it to 50% to 80%-100% strength. No measuring of PPM/EC/TDS needed.

Most lettuce plants are a light feeder, so I wouldn't give them more than 75%-80% strength. Even though you don't need to measure PPM/EC/TDS, the PPM/EC/TDS charts can come in handy to determine if the plants you want to grow are heavy or light feeders, or somewhere in between. By comparing the PPM/EC/TDS values of plants that like higher nutrient strength, and those that like it on the lower end, you can easily determine if your plants are heavy or light feeders, or somewhere in between. Thus decide whether you should mix your nutrients full strength for heaver feeders, or on the light side for light feeders.

Now with that said and at the risk of making it more complicated for you, the water volume of your reservoir is important too. The bigger the plants get the more water volume they need as well. Mainly because bigger plants consume more nutrients, thus will deplete the nutrients in that water faster. The more water volume there is, the slower the plants deplete the nutrient levels in that water. That will affect how often you would need to change the nutrient solution to maintain a complete balanced nutrient. I wrote this article to help explain these factors. What size reservoir do I need

P.S.
While you may get varying opinions, don't worry about asking to many questions, that's what forums are for.

newbie
 

Thanks for all the advice.
Hope I didn't goof up, as my lettuce that are started in the tank are not seedlings but 2- 3 inches tall, and Ive started then in 100% solution.
Do you think they will be ok?
Its 10 gal. tank, with 8 plants.
They look ok so far, but its only day four.
Also, after I test ph, Ive been pouring the little vial with test solution back in tank, is that ok, or should I toss it?

newbie
 

Also, Should there be a lot of bubbles from air pump under each plant, or does a few suffice?
Have Eco Air2 pump (126) minute, and three small air stones. About half the plants seem to be getting more bubbles then the others. I started with two stones and it seemed like there were more bubbles all around. Should I go back to just two?
Thank you, much appreciated.

newbie
 

And while I'm pestering you. I didn't reailize I was supposed to rinse clay balls that are in pots. Wii it be ok, only the bottom few are wet. Thank you.

Hello newhydro16,

I probably wouldn't want it to be more than 50% strength at that point, but if you don't see any negative effects like the leaves yellowing, burning tips, or burning roots etc. they should be OK.

That's a good water volume for 8 lettuce plants, even 1 gallon per plant would be good.
I would start seedlings in a prorogation system before transplanting them into the main system. It's a waste of nutrients, water, and space to start them in the main system. As an example, eight 2-3 inch seedlings don't need 10 gallons of water/nutrient solution. 1/2 gallon is more than enough for 8 seedlings that size. A prorogation system doesn't have to be complicated or expensive. It can be very simple. In fact I made one out of nothing but a used margarine container. I attached pictures of it. I just cut holes in the lid to stick the rockwool cubes in, put a little nutrient solution in it. Then just shook it a couple times a day to slosh the water around to wet the cubes. I also often just use a similar container but with holes in the bottom and using coco fiber as the growing media and just hand water it once or twice a day.

I would toss it. It doesn't serve any benefit to put it back in. That tiny amount of water volume won't make a bit of difference. I have never put it back in, and I haven't heard of anyone else doing that either. Honestly I don't know if doing so would eventually cause problems or not. I know it won't affect pH, but don't know if it would have any effect on the nutrients or not. But even if not, those few drops of water won't affect your water volume one bit to toss it out.

The general rule of thumb is the more air bubbles the better. It should look like boiling water at a heavy roiling boil. It's best if the air bubbles rise up right underneath the plants so the air bubbles make contact with the plants submerged roots. With that said, I have been able to grow good plants with far less air bubbles when my air pump wasn't working well and only put out half the that that it should. While the lettuce plants did well they would have done much better with more air bubbles. Here is a link to the system I was talking about Forth System. Here's a link to some pictures of how the air bubbles should look.

Water Culture system air bubbles
Water Culture system air bubbles
Water Culture system air bubbles


Rinsing the clay balls gets the clay dust off of them. The clay dust won't hurt anything, but may result in residue at the bottom of the reservoir. You can still rinse them if you want to. Just take the baskets out and dunk them in a bucket of plain water a few times. That should be enough to get the dust off. Just make sure you cover the top of the baskets with your hand to keep the clay balls from floating as you dunk the baskets.

newbie
 

GPS, Thanks for the great info. From what I can see you seem to be the go to guy here.
The plants look ok, and most of the roots seem to be growing.
The seeds were actually started in soil, and roots rinsed before putting in pots.
Ive since bought Rapid Rooter plant starter kit for my next batch. do you think that this product works well?
I will toss the ph liquid from now on. Great pics of everything, thank you.

Hello newhydro16,
I've been using this forum since back in 2009 when I first started growing plants hydroponically myself. There are some other members that help answer questions, but I don't think they check the forum regularly. I try and check it at least once a day for new posts, so I wind up feeding most of the questions. I try and help people as much as I can.

I haven't used the rapid rooter plugs myself, but their similar to the jiffy pot plugs. The rapid rooter plugs claim to provide better aeration to the roots, but their still very easy to water log. Many people have issues with them becoming to waterlogged. So if you use them make sure you don't over saturate them. You only need them damp, not dripping wet. If they drip out water when you pick them up or slightly squeeze them, their to wet.


I personally prefer to use coco fiber to start seeds in. I just take two short used plastic whip cream (or butter) containers I cleaned out. Make a bunch of small holes in one of them. Put some damp coco fiber in it, and pack it down like potting soil, put my seeds in and cover them with another 1/4 to 1/2 inches more of coco fiber. Fill the other one with water and gently sit the one with the coco fiber and seeds in it. This gently waters/soakes it from the bottom. I let it completely saturate for a few minutes, then take it out and drain.

Once it's drained, I place it right back into the container I used to water it. This time it's empty, this keeps it from dripping on the floor in the house or anywhere I set it down. I'll hand water it like this once or twice a day. When the seedlings sprout and start growing their first true leaves, I'll use a very diluted nutrient solution. I'll mix up one gallon of full strength nutrient solution and keep it in a water bottle. Then just pour in a small amount in the container and dilute it with plain water when I water the plants. I don't even measure it I just eye ball it (10%-25% dilution rate etc.).

I don't even check pH because it's to small of an amount of water at this point. I'll check and adjust pH for the gallon of nutrient solution, but when you you dilute it by adding 75% to 90% more water in the container when you water the plants, that can change the pH depending on the pH of the water source. That's to small of an amount of water to check and adjust, especially to much work to do it every time so I don't bother. If you really wanted to you could get another gallon container for just plain water and pH adjust that water to use to dilute it with. But I rarely ever bother doing that.

newbie
 

GPS,
Thank you, and for the pictures. Ill keep the coco fiber in mind after Ive tried the rapid rooter plugs.Ill see how I make out with them. How high should my lights be from the lettuce? I'm using the square colored leds. Currently have them about 10 inches from them.
PH has been around 6, but while I'm only on day six, I'm not seeing the growth that people claim they have in such a short time.
Plants look ok, I'm wondering if I'm getting enough air bubbles, some of the plants aren't getting a lot. Would I be better with my pump which has two outlets, run the lines into one and just have one stone, currently have one line teed off in the tank, so there are three stones, but I'm wondering if these stones I got,(cheap, ebay) are not the best.
Really appreciate you getting back to me. Thanks again

newbie
 

Also, when I mix new batch of nutes, do I still need to add the flora bloom, seeing as this is lettuce I'm trying to grow. Thanks.

Hello newhydro16,

LED's aren't the best lighting to use in my opinion. Mainly for two reasons, first good quality LED's aren't cheap, and won't really save you much of anything in electrical costs. The break even point between higher equipment costs and lower electrical costs is generally 5-10 years. Personality I'm not going to wait 5-10 years to break even and start saving money. Second, the quality of the LED's for growing plants is all over the place. Not only are there thousand of manufactures making them, but the quality and wavelengths/spectrum vary greatly from one manufacture to another. Not only that but you can't tell good quality LED's from low quality ones by price either. The market is flooded with low quality LED's (mainly from china) that they charge high prices for. So you really have to do your homework on the specific lights you get.

But just like with Florescent lighting, you want LED's to be as close to the plants as possible without burning the plants. Again the quality and wavelengths output of the LED's lights are going to make a big difference in the amount of usable light the plants get.

I don't know who your talking to who claim great results in 6 days, and I don't even know the progress of the plants your growing. So I cant say if they are growing slowly or normally. However first, six days isn't very long, second lettuce plants usually start off slowly. Their very tiny seeds. Third if I remember correctly you said you transplanted them, and it generally takes a about 4-7 days to get over transplant shock.

But if they are growing slowly there could be many reasons. Some of the typical reasons are not enough light, temperatures (both air and water temps), humidity levels, moisture levels to the roots, oxygen levels to the roots, nutrients, even pests and/or disease. I would have to know more about the details of your system and growing environment to see if there are any problems.

First without pictures I can't tell much. I gave you pictures of what it should look like in a previous post. Second. air stones are typically cheap, depending on size usually run from 1 to 3 bucks. However they can clog from time to time. I get them at Wal-mart for about $2, but you can get them anywhere they sell pet supply's.

Lastly, no mater how you run the lines or how many air stones you use, you can't make the pump be able to put out more air. Sure if you run both lines into one air stone you will see more air bubbles from that air stone, but only because your pumping more air through the air stone. Kind of like if you have two glasses each filled half way with water, then you pour the water from one glass into the other. Now you have one full glass. But not because you made more water, it's still the same amount of water, just in one glass instead of two.

If your air pump has two outlets, use both of them. Use one air stone for each line. Don't split the line to connect more air stones, that wont make more air bubbles. It just dilutes them because it has to split the air output to more stones. You'll notice in the pictures I posted earlier there are two air lines coming from the pump. Each air line is connected to one air stone. so there are two air stones in the bottom of the bucket and one twin output aquarium air pump for 30-60 gallon fish tanks supplying all the air.

I'm' going to assume you' referring to the General Hydroponics Flora series nutrients. Not general Hydroponics Flora Nova series. Their two different nutrient lines. With the Flora series nutrients it has three parts Gro, Micro, And Bloom. Yes you need all three parts to work. You still need to use the Bloom, but not as much of it. For lettuce I would mix it 15 ml Gro, 10 ml micro, and 5 ml Bloom per gallon of water for full strength nutrients. (5 ml is 1 teaspoon, 15 ml is 3 teaspoons or 1 tablespoon).

newbie
 

Thanks again,
Ill get rid of the tee inside the tank, just run two stones one off each line.
Lights are blue/red, from ebay, 45 watts, one was $50.00, other $35.00, and yes looks like from China.
Ill try and be patient, they look healthy enough.
Thanks for the help, appreciate you taking the time to share your knowledge.

Hello newhydro16,
I would use florescent lights myself. I don't know what your spacing is or how much coverage area your trying to get out of the two 45 watt LED lights. But each 45 watt light probably wont cover more than one sq foot each. Have a look at this video Low Watt LEDs vs T5 Grow Lights. For lettuce you'll need a minimum of about 35 watts of LED lighting per sq foot. However with florescent lighting you only need about 27 watts of light per sq foot. That's less wattage for florescent lighting. Four 4 foot T5 bulbs is enough to easily cover a 2x4 foot space and plenty to grow lettuce. each 4 foot T5 bulb is 54 watts x 4= 216 watts total. 216 watts divided by 8 sq ft =27 watts per sq foot.

With that said not all LED's are manufactured the same. Some will preform better, and others worse. To understand why you first need to understand wavelengths of light. Wavelengths of light are different than spectrum of light. Wavelengths are specific, and spectrum's are a range. Red and blue are spectrum's (ranges) of light that are made up of specific wavelengths. Think of it like a radio. FM radio is a range/spectrum of individual wavelengths. Radio stations broadcast on a specific wavelength, and there are a lot of individual specific wavelengths within the spectrum of FM radio. The same holds true for light. You can also think of it like shades of light. While Red is a color there are hundreds of shades of red. Red is the spectrum, but each specific shade of red is a wavelength within the spectrum.

You can't tell how many individual wavelengths of light there are in a specific color. You know you see red or blue, but you can't tell how many specific wavelengths are present in what your looking at, nor can the human eye tell how strong those wavelengths that are there are. So in other words while one red LED light may look just like another, they can be vastly different in actual light output. This is why you really have to research the manufacture of the LED lights to find out if not only do they know what they are doing in manufacturing them, but if they do growth rate, as well as growth quality testing comparisons. Otherwise it's just a crap shoot.

You should also know that each specific wavelength of light affects plant growth differently. Even though it's not commonly known, plants even use wavelengths from the green spectrum of light to build structure. Each individual wavelength of light is used differently by the plant, so they need a good range of wavelengths to grow properly. Many LED lights result in abnormal growth because they don't provide enough range of wavelengths. Again this is why you really need to research the manufactures of the LED lights.

P,S.
You'll be able to tell if your plants aren't getting enough light by looking at the growth. If their getting long and leggy, their not getting enough light. If their growing abnormally small and thin leaves their not getting enough light. If the stems aren't getting thicker and their continuing to grow tall like their going to fall over because the stems can't support the weight, their not getting enough light. Being able to tell if their getting enough range in the wavelengths of light is harder to tell since many of the symptoms can be a result of nutrient balance and/or pH as well.

Both are 45 watts each seem to cover my dwc more then enough.
All I can tell from description is 660 wave lengths, spectrum ratio, red blue = 2.25.1
I admit, no clue here.
Thanks for your help, and patience with me.
ph seems to be holding about6.0

Hello newhydro16,
LED's have a very short usable distance for plant photosynthesis. The light intensity plants need for photosynthesis is very different than humans need to see with. Sounds like a pretty narrow wavelength range with one specific wavelength (660 nm). The wavelength range for the red spectrum is from about 610 nm to 740 nm, and the blue spectrum ranges from about 425 nm to 520 nm. The green spectrum ranges from 520 nm to 565 nm.

What Wavelength Goes With a Color?
Electromagnetic spectrum

But as long as you already have them see what happens. Even if the LED's give good growth quality, two 45 watt lights won't be able to grow many plants. If you plan to grow much lettuce you'll need more coverage area and will be much cheaper using florescent lights. If you do get good growth quality from those LED's, they would be good for starting seedlings in a prorogation system. You wouldn't need more than 2 or 3 sq feet for a prorogation system to start seedlings. That way you can rotate new plants into the main system as you harvest. That not only shortens the time the plants need to grow in the main system by 2-4 weeks and makes it much more productive. But also separates the seedlings from the larger plants because the nutrient strength for seedlings is much lower than for larger plants. If you plan to have a continual supply of lettuce you'll want to start seedlings in a prorogation system and rotate plants anyway.

newbie
 

Thanks GPS,
sounds like a good idea

Did you sprout from seed? What type of lettuce
 

I bought a big bag of black seeded simpson lettuce seeds from the hardware store.

They were easy to sprout in grow block on a tray and took root in severe hot weather in my outdoor system.. But the lettuce was really leafy

I want to find some real good iceberg or romaine seeds.

newbie.. GPS has said many times here.. the only way to learn is try
I am looking forward to my second year of growing

I believe hydropnic gardening will become more prevalent with climate change

newbie
 

Yes, from seed, Buttercrunch.
I had them in soil until I decided to try my hand at hydroponics, so I carefully pulled them and rinsed them. Have to admit, I have spent a lot more then I thought I would on getting going.
Water temp is a little low I have a heater ordered, and, GPS, I ordered a two bulb t5 light.

Hello newhydro16,
Growing your own produce hydroponically is all about being economical. Pot growers make $1,000 to $2,000 a pound for their product so they don't have to care about being economical. But if your going to grow produce, you need to think about being economical, everything from the choice of hydroponic system and how you design it, to the type of growing media, to how you test pH, the nutrients and pH adjusters you use, and especially your lighting. It's all about maximizing your resources, and minimizing your costs.

But don't be discouraged, you learn by doing, and you'll learn more about how to be economical as you go as well. Almost every new hydroponic gardener winds up spending much more than they need in the beginning. Most Hydroponic shop salespeople don't help you be economical much either. They aren't in the business of helping you be economical, their in the business of selling as much product as they can. So they try and convince people you have to have the best of everything. Some of the sales people don't even know much about hydroponics to begin with and only work there. I'm not saying that hydroponic shops and/or all the people that work there are crooks. But they do have an agenda, and that is to sell products so they can make money and stay in business.

So it takes time to learn what you don't actually need and what you do need, as well as sourcing out economical products, and how you can repurpose things to build hydroponic systems with. The first lesson in being economical is only buy what you have to at a hydroponic supply shop. General that means only nutrients, pH adjusters, pH drops, possibly growing media depending on what type your using, and only if you have to and your not using florescent lights artificial lighting. Manufactures typically feel if you add the word "hydroponics" to the product, it's automatically worth twice as much. Even when you have to buy from a hydro shop, when it comes to nutrients and artificial lighting there's often a big difference in price depending on where you buy from. Just because it's expensive doesn't make it better. It's all about sourcing out the right vendors.

The optimum water temperature for plants is between 68 and 75 degrees Fahrenheit. That's just the optimum temperatures, you can easily be a little above or below that without any problem. if the water temps start regularly going below 60, and/or above 82-84 you'll want to start worrying about it. Lettuce is a cool weather plant, so you'll want your water temps to be on the low end (under 80).

I don't know where you ordered your heater or lights from, but a inexpensive fish tank heater you can get at any pet supply place and can get for $10-$20 is all you need. You can even get them at Wal-mart in their pet supply section. T5 lights you can get at any hardware store like Home Depot and Lowe's for about $35-$40 for a 4 foot twin bulb fixture with the bulbs included.

P,S.
One twin bulb T5 wont cover more than a one foot wide area. The maximum coverage area would be 1 foot wide by the length of the bulb.

newbie
 

Thanks GPS,
Heater came yesterday, and while I know you don't recommend the cheaper testers, my ppm keeps dropping, so I think as long as I have the heater to install, Ill change my solution today. Its been about two weeks since I started the dwc.

newbie
 

Also, I'm finding conflicting numbers on the ppm for lettuce. One says 280-560,another 560- 840.
What are your thoughts?

Hello newhydro16,
I don't recommend using a EC/TDS/PPM meter at all unless you have money burning a hole in your pocket. It's a fun toy, but simply not necessary. As for the conflicting PPM ranges. This is part of the reason relying on EC/TDS/PPM is a mistake. First of all PPM will vary from one region of the world to another, and from one manufacture to another. EC is the standard, PPM is a conversion from EC, Each manufacture uses a different conversion. Second and the biggest reason I don't even use EC/TDS/PPM meters is there are so many variables that affect nutrient uptake and optimum EC/TDS/PPM values that it's impossible to list them all. Third there are hundreds and sometimes thousands of varieties of any particular plant. There are thousands of varieties of lettuce in particular. They all have different optimum EC/TDS/PPM ranges, and that's even before considering the environmental factors that will affect the optimum range as well. Relying on EC/TDS/PPM readings and charts is a mistake. The charts are just meant to be a general guideline.

But many people begin to rely on taking a measurement and think that as long as the readings are within the recommended range, their nutrients are good, as well as balanced. But nothing could be farther from the truth. Why do people think that? Because that's what the salespeople selling them the equipment tell them. They simply don't know how to tell when a plant is healthy or not by looking at it, and easier than learning to identify the signs of over and under feeding. So they just get used to using the EC/TDS/PPM meters as a crutch. When they use the meters as a crutch it takes much longer to learn to identify problems by looking at the plant. And looking at the plant is the only real way to tell if their healthy, as well as if their being over or under fed or not.

My recommendation is to fallow the nutrient manufactures mixing instructions, and mix them to about 80% strength. (10% to 25% for seedlings, 25% to 50% when they get a little bigger, then up to 75% to 100%). Once you begin to learn how the environmental factors like temperature, humidity, and even duration and and intensity of light will affect the nutrient uptake, then you may want to adjust the nutrient strength based on the environmental factors as well. Like even weaker during hot and/or dry conditions when the plants drink more water than take up nutrients. Or a little stronger in high humidity when the plants can't drink up water as easily etc.

A general rule is 80% strength is typically just fine, especially for plants that are light feeders like lettuce. If you don't know if a plant is a heavy feeder or not, then the EC/TDS/PPM charts will help you. The plant types with the higher ranges are heavier feeders, the plant types with the lower ranges are lighter feeders. Another sign is the color of the foliage. Plants with darker green foliage are typically heaver feeders than those with a lighter green foliage. One lettuce plant may have light green foliage, and another variety may have darker green foliage. The variety with the darker green foliage would be a heavier feeder than the variety with light green foliage.

Flurescent Better than LED
 

GPS.. I was curious.. I know there are 200W CFL's out there.. are they effective? Flourescents have a better spectrum?

Hello shillamus,
It depends on what your growing with it and how you have things set up. CFL's are the same thing as T5 florescent lights, except their more compact. hence the term CFL (compact florescent light). CFL's have the ballast in the base of the bulb, straight tube florescent lights have the ballast in the light fixture.

Weather their compact or straight tube, all florescent lights have the same issue. The usable light range is very short. The luman drop off rate goes way up beyond 2 feet from the bulb. In other words at 1 foot from the bulb your getting about 85% of the usable lumins/par to the plant foliage, at 2 feet your getting more like 60%, at 3 feet from the bulb your only getting about 25% of the lumans/par reaching the plant, at 4 your getting basically no usable light. Same goes for LED lighting.

While a 200 watt CFL will concentrate more lumans/par in one area, the coverage area is smaller. As an example four, 4 foot T5 bulbs equal 216 watts and will cover 8 sq feet of area. While a 200 watt CFL will only really cover about 4 sq feet. So the wattage is about the same but the coverage area is cut in half. You don't need 200 watts per 4 sq feet to grow lettuce. It would grow faster because of the higher light intensity. but not really worth all the extra electricity. You would be better off with the larger coverage area and growing more plants.

With that said fruiting plants take about twice as much light intensity (par/lumans) to support the fruit. While it is possible to grow fruiting plants with florescent lighting, it's not cost effective. Watt per watt your much better off using HID lighting to grow fruiting plants, especially large ones like tomatoes.

As for spectrum of florescent lighting, higher wattage doesn't mean better spectrum. It means higher light intensity (output). Unless the manufacture is selling their lights in the hydroponics industry they don't usually provide a wavelength (spectrum) chart for comparison. It's not that florescent bulbs sold in hydroponics shops are necessarily better than standard bulbs and that's why they provide the charts. Manufactures selling their florescent bulbs for household and shop lighting don't need a wavelength chart because people buying them for that reason aren't comparing wavelengths. They compere the color of the disable light by the K value. They typically range from 2400K to 6500K. The lower the K value the more of the red spectrum the light puts out, the higher the K value the more of the blue spectrum there is.

newbie
 

Thanks again GPS told you Id be a pain in the butt

Hello newhydro16,
While helping people is time consuming, I don't mind trying to help people who want/need the help. The way I look at it is if I help you be successful you can help someone else be successful later. That's what makes the world go around.

How about using 150 watt HPS lights instead of 4 tube, 4 foot fluorescent lights? I use a Sun Systems 315 watt LEC for the grow area, and I am thinking about adding several Sun Systems 150 watt HPS lights. Those 150 watt HPS lights are less than $60 each, cheaper than a 4 foot, 4 tube fluorescent light. I have 4' x 2' metal shelves, and I was thinking of installing one 150 watt HPS above each shelve.

Hello Davephan,
It all depends on your spacing, location, and how much your growing. HID lighting will give off more heat so they need to be farther away from the plants which isn't a problem since the luman drop off rate is much lower with HID. However if your growing in stacked rows like shelves the extra height needed may be an issue. Also With a 4 foot florescent light you get even lighting along the the 4 foot length. Where if you used one Hid bulb in the middle, the plants in the middle will get a much higher light intensity, and the ones around the edges would get lower light intensity, so the growth rate wont be even. You also may have an issue with light shading. That is the plants closest to the light blocking/and shading light from the plants farther away. With multiple bulbs you can reduce light shading problems, as well as get even lighting over the whole coverage area.

But if your looking for more coverage area, HID lighting certainly is the best option. It all depends on how much coverage area you need. That all comes down to planning. Deciding on how many plants you need to grow, how much coverage area you need, where you will be growing, how you will be growing. Even controlling temperatures all come into play.

But ultimately you could easily get more coverage area out of using multiple low wattage HID lights than florescent lighting. As an example 4 T5 lights (216 watts) would easily cover a 2x4 foot space (8 sq feet), but 2, 100 watt HID lights spaced evenly could cover a 6 x 3 foot space and could more than double that coverage area (18 sq feet) using about the same wattage.

P.S.
Do the $60 lights your talking about come with the light fixture and ballast? I'm aware of a 100 watt HID light that comes with the fixture and ballets, but runs about $114. Mini Sunburst MH w/Lamp, 100W