The pH of the fertilizer blend in your water is on the acidic side if I understand what you are saying:

If I put the correct amount of nutrients in the water the PH is WAY low

But it is confusing the way you relate what's going on because you say to the effect you are 'using the nutes in lieu of pH down'. So does this mean you put them in at half strength and then keep the pH down by regular supplementation of additional fertilizer?

There is nothing wrong with using small amount of fertilizer to 'adjust pH' so it isn't completely wrong, as long as the strength of the nutrients isn't pushed too much over the recommended strength. And, if you just started and have a situation of half strength and add ferts to maintain the proper pH I say great job. Except once you've accumulated a full dose of ferts, now it's time to use a better adjustment method, because plants will begin to experience some toxicity from some of those nutes in excess.

The question you ask, bicarbonate, can't be answered because your water is an unknown. It sounds to me like the water isn't very alkaline since the fertilizers alone brought it down in pH LOW you say, I'm assuming below 5.5 or so from you comment. Alkaline is not the same as pH>7 by the way. The amount of alkalinity depends on likely, how much bicarbonate is *already* in your water. Bicarbonate itself isn't a problem except the wrestling match it may make buffering pH the way you may not want. The problem is baking soda (which is an industrial chemical produces from ammonia and salt and *not* any more natural than other pH downs), contains sodium and sodium becomes toxic above certain amounts. So to be safe in *relatively low* sodium mineral water you can use around a half gram per gallon (0.7 gram per gallon gives 50 ppm sodium which when added to your water's soda content will start to be toxic in hydro) in a pinch and then you need to find something else, whether it be a pH up of potassium hydroxide, magnesium hydroxide, calcium carbonate, potassium silicate, etc. Usually minimal pH up is needed in most situations since most fertilizers as the plants eat naturally have pH drift upwards.

Different plants respond differently to sodium toxicity. Tomatoes can take a lot more than strawberries, for example. Also we don't know how much chloride is in your water. The more chloride the more sensitive to salt the plants get.

To get a better answer, you need to have an analysis of your water's contents and then we could be more sure what to do.

This post was edited by PupillaCharites on Fri, Oct 18, 13 at 19:41

I would just buy a gallon of the ph down. It lasts a long time.

I don't think the airstone is worth the effort if you are already moving a decent amount of water. The flow turns over the surface area, and that creates effective aeration.

Your tomato plant isn't going to make any tomatoes without supplemental light, especially at this time of year. You might try again in the spring when the days are getting longer.

The spiral CFL bulbs that are "150 watt equivalent" can be fashioned into cheap grow lights. Cool white is best for green, leafy growth. The bulb is about $8, a cheap socket is about $2, and a $1 extension cord can be wired as the plug. Aluminum pie pans make good cheap reflectors. $12 of materials will do the work of a $150 "grow light."

Even with good fluorescent lighting, the tomato is still probably a lost cause. You might be able to grow a miniature cherry variety like Tiny Tim, but it will be unimpressive without the more expensive high-intensity lighting, which is hps or metal halide. A 150 watt high pressure sodium, commonly found in outdoor security light fixtures, will grow at least some decent cherry tomatoes. Choose your tomato variety carefully - you probably want a compact-growing dwarf.

thanks for the responses, sorry I haven't responded again. I did end up getting ph up and have been using the required amount of plant nutrients. they seem to be thriving. my next step is to get the extra lighting and I think they will de better. I too don't expect my tomato plants to actually grow any fruit but the way I look at it. I just started doing this a few months ago and my plants are actually thriving. way better than I was ever able to do with dirt.

now my current issue.....I have read about and used peroxide / water/ air stone to clean the roots. then rinsing well. it works awsome but my water keeps aquiring algae. I have heard about cleaning the system (no plants) with bleach water. should I? how strong? is that going to help or should I do something else? thanks again

Light is hitting your nutrient solution somewhere. That's what makes algae. Blocking the light with something like aluminum foil is the only real algae control.

People have different ideas about sterilizing reservoirs. I have had bad results with it, but that doesn't mean it doesn't work for some people. My method is to try to build up the right bacteria balance, and then let it take care of itself. I use fish tank water, and over time, a gross-looking goo of composting fish manure forms on the bottom of the reservoir. It sounds disgusting, but plants love it. Cleaning the reservoir with bleach would be catastrophic to all of my good bacteria.