Hydroponics Online Home Home Store Blog Forums FAQs Lesson Plans Pictures

Go Back   Hydroponics Forums Discussions > Hydroponics Discussion Forums > Hydroponics

Beginner Question: Air pump?


Reply
 
Thread Tools Display Modes
  #1  
Old 04-26-2016, 10:30 PM
malangon malangon is offline
Junior Member
 
Join Date: Apr 2016
Posts: 8
Default Beginner Question: Air pump?

I am brand new to hydroponics and I'm just starting to experiment. I built 2 "raintowers" which are essentially 6 foot tall PVC structures which rain/drip the solution down on the inside.

My question is: In doing some further research, I wanted to add something in addition to my raintowers (which I haven't fully implemented yet).

My idea was to construct a system using horizontal 4 inch PVC with net pots and a system with a tank that runs water through the PVC pipes. Forgive this basic question, but two issues confuse me which I can't seem to get a straight answer:

1) Should the roots stay submerged with the water constantly flowing or do I put this on a timer and do a "ebb and flow" type setup? Why one way or the other?

2) I have seen systems with an air pump and air stone. I get it that O2 is important, but is it important enough to to to incorporate an air pump or is that an optional item?

Thanks!

Reply With Quote
  #2  
Old 04-27-2016, 04:30 AM
GpsFrontier GpsFrontier is offline
Senior Member
 
Join Date: Mar 2009
Location: Lake Havasu AZ.
Posts: 1,831
Default

Hello malangon,

Quote:
1) Should the roots stay submerged with the water constantly flowing or do I put this on a timer and do a "ebb and flow" type setup? Why one way or the other?
I'm guessing the reason your not getting a straight answer is it's not a straight right/wrong question. Especially the way you posed the question, because there are a lot of other variables to consider that would make differences. There is no right or wrong here, just preferences. It's not about which way is right and which is wrong, it's more about knowing those variables, and how well you design the system to accommodate the variables and needs of the plant. You could build two identical systems, use identical nutrients, place identical plants in each, and run one as a flood and drain (ebb & flow), and the other as a recirculating water culture system (the roots stay submerged with the water constantly flowing).

Then after a month of growing will you see identical plant growth? Likely not. While they will probably be close, you'll likely see some difference. However, if you know the differences between both types of hydroponic systems, what makes them different, and understand the needs of the particular plants your growing in the hydroponic systems. Now you can make adjustments to either system to better accommodate the plants needs so you can get close to identical plant growth in both systems. So you see why it's not a cut and dry this is better than that question?

Now if you gave me all the specifics about the type of plants you plan to grow, how many of them you want to grow, the space you have to grow them in etc.. Then I could give you more of a straight forward answer as to what I would do, and why I would do it that way verses another way. It's always going to come down to preferences, but if I know specifics, I can give specific reasons for my preferences.

Quote:
2) I have seen systems with an air pump and air stone. I get it that O2 is important, but is it important enough to to to incorporate an air pump or is that an optional item?
Oxygen is very important to the plants, some plants more than others. As an example: plants that need well draining soil, and/or don't like wet feet cant tolerate saturated roots (suffocating roots). So good aeration is more important to those type of plants compared to plants that don't mind wet feet. All plants need moisture in the root zone. But the term "wet feet" is referring to water saturation in the root zone. Plants that need well draining soil, can't tolerate wet feet (water saturation) as well as plants that don't mind wet feet. If the plants don't get enough oxygen to the roots, they suffocate. Symptoms can range from slow growth, to wilting, to root rot, to death.

As for the question about is it important enough to incorporate an air pump, or it just being optional. Again, it all comes down to how you design your hydroponic systems, and the plants specific needs. Here the type of hydroponic system makes a big difference, since what makes the type of hydroponic systems different is in the different ways they supply water, nutrients, and oxygen to the roots. But how well the system supply's these elements is in how you design it. An air pump isn't the only way the plants roots can get air/oxygen.

As an example: in a flood and drain system, the flood and drain cycle makes a big difference in how much air/oxygen the plants roots have access to. The longer the roots are submerged, the less oxygen they can get. Say you have a 30 min on, and 30 min off cycle time. 50% of the time the roots are submerged and the only oxygen the roots can get is dissolved oxygen in the water. But when the system drains, fresh air is sucked in, and the roots then have access to air as well as dissolved oxygen in the water. Changing the cycle time from 30 on/off to 15 on, 30 off, will increase the amount of air the roots can get by 25%.

Even changing the cycle time from 30 on, 30 off (50% submerged), to 15 on and 15 off (50% submerged) will increase oxygen levels in the root zone. I know your asking how. The same way you would suffocate by putting a bag over your head. Even though there is still air in the bag, the oxygen will become depleted, and thus you suffocate. Each time the water cycle's, it sucks down fresh air into the root zone. The longer the air remains there the more depleted the oxygen (as well as co2) becomes. By using shorter, but more frequent cycles, you suck fresh air down into the root zone twice as much. In other words, you would still have a 50% submerged rate, but you would get twice as much fresh air getting to the roots. How quickly it becomes depleted depends on a lot of factors like plant size, root zone space, temp's, etc.. But the point is just changing cycle times in a flood and drain system can change root zone oxygen levels, and just one of the ways to increase oxygen levels by system design.
__________________
Website Owner
Home Hydroponic Systems
Reply With Quote
  #3  
Old 04-27-2016, 03:46 PM
malangon malangon is offline
Junior Member
 
Join Date: Apr 2016
Posts: 8
Default Update

Thank you so much for the detailed reply. I have downloaded every book I can get, but it's odd that there doesn't seem to be a real straightforward answer on some of my more basic questions.

Let me try to be very specific and would love your input:

I'm putting together a crappy outdoor greenhouse (PVC and plastic). I was planning to use a large rubbermaid storage container for a nutrient solution and pump it into 4 foot lengths of 4 inch PVC tubing. I was thinking each shelf could hold two of these tubes and I would end up with 4 tubes.

I would love to plant lettuce, spinach, peppers, basil, and tomatoes. Note: this is based on my own eating preference rather than any hydroponic expertise.

I expected to use a single pump to pump the solution into one tube on each side and let gravity allow it to flow through and drain back into the reservoir.

Comments, feedback? Will I end up with yet another round of dead plants and a failed foray into a new hobby?

4 inch tube, 3 inch netpot, clay pebbles, flora grow nutrients.
Reply With Quote
  #4  
Old 04-27-2016, 11:43 PM
GpsFrontier GpsFrontier is offline
Senior Member
 
Join Date: Mar 2009
Location: Lake Havasu AZ.
Posts: 1,831
Default

Hello malangon,

First, I don't know what your location is like, but one problem you can encounter with using the 4 inch tubing is heat buildup in the root zone. Especially if the tubing is in direct sunlight. Ran as a flood and drain system cool water floods the tubing and root zone, but in the off cycle the cool water drains back to the reservoir, and sitting in the sun heat builds up in the root zone. Then it cycles cool water through the tube again during the on cycle. So you wind up with cycles of cool and hot in the root zone. Now constant flowing water can help alleviate the heat buildup in the root zone, but the just like when cycling it, the reservoir temps will slowly rise as well. So if you think there may be a problem with heat build up, you may want to think about insulating the tubing/root zone. I don't know if you know but in case not Nutrient Solution and Root Zone Temperature is Important, that was my first major lesson when I started growing hydroponically.

Second, I wouldn't grow all those plants in the same system. The reason is because you have many widely varying plants. Some flowering and some not, some large and some small in comparison, some long term and some short term plants.

Third, I wouldn't try and grow tomato's or peppers in a 4 inch tube. Tomato's and peppers are large plants that will have a large root mass. While plants will always try their best to adapt to their environment, the large plants will quickly outgrow such a small root space, and eventually clog the water flow in the tubes. I prefer to grow large plants in a drip system because I can easily make the root space any size I need, and you don't need to flood the entire root space to wet the roots. I prefer to use coco chips as a growing media for three reasons. One, because it holds moisture well withough't becoming saturated, and because the larger partial size of the chips leaves larger air gaps between the particles. Giving better aeration to the roots for the best of both worlds (water and air). Lastly because it's cheap

Fourth, lettuce is a short term plant, so depending on how much of it you plan to grow, I would probably grow it in it's own system. It would be a good candidate for the 4 inch PVC tube system you plan on. Although I would use ADS tubing instead. ADS tubing is black on the inside to block light, and white on the outside to reflect light. Most lettuce do well in water culture systems, so running it either way (as a flood & drain system, or recirculating water culture system) should work fine. If running it as a recirculating water culture system I would keep the water level below the baskets to keep an air pocket between the plants and water level (similar to a NFT system but higher water level), simply because it's hard to get air stones/blubbers in the tubing to aerate it. If running it as a flood and drain system, I would try an keep the on/off cycles short to maximize air intake, and maximize water circulation/movement.

If running it as a recirculating water culture system, There isn't to much need for an air pump in the reservoir because the water is circulating 24/7 and the falling water helps aerate the water itself. Also if you leave an air gap between the plant baskets and water level, the plants have a secondary source of air/oxygen. If running it as flood and drain system, I would use an air pump in the reservoir not only to help aerate the water, but more importantly to circulate the water during the off cycle and help reduce the likelihood of pathogens gaining a foothold in the system.

Fifth, as for the Spinach and Basil, these are both non flowering medium size plants. Well they do flower, but you don't want them to flower because your growing them to consume the foliage. Again while you can easily design any type of system to grow these well, I think my preference would likely be in a drip system. Mainly because their long term plants, and simplicity. Also I think the spinach likes to spread out like ground cover, and I can easily provide more surface area for it to do that with a drip system. However depending on the space I had to put them, I might grow them in a low pressure aeroponic system. Similar to what you described as your raintowers.
__________________
Website Owner
Home Hydroponic Systems
Reply With Quote
  #5  
Old 04-28-2016, 10:43 PM
malangon malangon is offline
Junior Member
 
Join Date: Apr 2016
Posts: 8
Default Update

Great info, thanks again. Also enjoyed your website (followed the link in your signature).

One last question if I can impose;

Given the system I described, running a flood and drain, what plants would be your go-to choices for that setup?
Reply With Quote
  #6  
Old 04-29-2016, 12:37 AM
GpsFrontier GpsFrontier is offline
Senior Member
 
Join Date: Mar 2009
Location: Lake Havasu AZ.
Posts: 1,831
Default

Hello malangon,

Quote:
Given the system I described, running a flood and drain, what plants would be your go-to choices for that setup?
Any plants that's root systems wont become to cumbersome, in other words small to medium sized plants (up to about 4 feet tall and wide). For medium sized plants I would space them farther apart than small plants. Not just to give the plants room to grow withough't crowding, but to give the root systems more space as well.

As for a go-to plant choice for that system, to be honest I cant say I have any. Over the years I have learned to design hydroponic systems based on the plants needs, and available space and resources. Not to design the system first, then try and to adapt the plants needs to the hydroponic system. For me designing the system first is doing things backwards. I start by deciding on what I want to grow, how much of it I want to grow, take into consideration the space available to grow it in. Once I have those things worked out, I can start deciding on the best type of system to grow them in, and start designing it.

In the past I have used a system like the one you described to grow peas in this system: third system. While I would consider pea plants to be on the large side of medium sized, the roots didn't cause too much problem with clogging. I did have to do preventative maintenance to keep the flood and drain openings from clogging each week. Pea plants are a vine, and I do like that design for vines. However if I were to do it over again, I would make some changes. But that's what it's all about, you learn by doing.

__________________
Website Owner
Home Hydroponic Systems

Last edited by GpsFrontier; 04-29-2016 at 12:41 AM.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 08:00 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2017, vBulletin Solutions, Inc.