Thought I would post what I have found out so far about adding calcium for tomato's.
Some forms of tomatoes are notoriously heavier calcium feeders than others. Heirlooms in Hydro, are typically more heavy on the Ca feeding. If you have a greenhouse hybrid, they are typically less heavy feeders on the Ca. Since Calcium and Magnesium are important in allowing the uptake of the other ingredients, you want to make sure you supplement the plants needs in those areas. Calcium effects the plant's ability to uptake all sorts of
nutrients. This is why it's recommended to supplement with Calcium when growing plants that consume a lot of it (such as tomatoes).
You most likely won't be able to pinpoint a Calcium deficiency on the plant, because it can appear as a plethora of other deficiencies. Nutrition in Hydroponics is a building block philosophy. Once you have low concentrations of one element, the rest react differently to other elements, and this can start a chain of lockout.
There are CaMg supplements on the market and they would be the best way to specifically add Ca/Mg without raising the concentrations of other nutrients. General Hydroponics makes one called
CaMg+ that runs about $15 for quart. Starting low and working up, like 5ml/gallon. Then if you notice a need for more, add more. until you find the zone that's right for them. I haven't looked into other manufactures of this supplement though I'm sure their are many.
As for the dolomite, I have not had time to find out much more about it. Although I do have a few of concerns with it. First, I'm not sure if it's water soluble or not. If it's not completely water soluble the plants wont be able to use it. Soil nutrients generally breakdown/biodegrade in soil slowly converting it into a water soluble
nutrient. But without the soil to break it down, it would need to be water soluble to begin with.
Second, if you do use it, I would not add it directly to the
growing medium. But rather use it as an additive to the nutrient solution instead. There would just be no good way to control the amount and concentrations. If you didn't get the exact amount right from the start you can add way to much, possibly doing more damage to the plants than good. And because as it dissolves you would be making a higher concentration of it in the nutrient solution with every cycle, resulting in a constantly changing concentration of it. If you just add it in the nutrient solution directly you wont have either problem. Also if there is a problem with it you don't need to change all your growing medium, just the solution.
Lastly, I'm not sure what it would do to would PH levels. In the description on the link it says
"Corrects Soil PH." This tells me it's not pH neutral, and I would fear that you will be constantly trying to adjust the pH.