Hydropodics ~ TechnoTalk

Some Misc. Q & A

We are by no means 'experts' about hydroponics, but we have learned some things along the way and are happy to pass these along to any who may benefit from these ideas and links.

  • What About Aeration?

    Plants grown hydroponically need oxygen in the water to thrive and take in nutrients. Well-oxygenated water favors good bacteria as well. Poorly oxygenated water favors root aphid development (yuck).

    Temperature affects how much dissolved oxygen the water can hold: the hotter it is, the less oxygen the water contains, so we insulate our water reservoirs so they don't get too hot or too cold. The ideal temperature is between 65-80 degrees Fahrenheit.

    One of the best ways to get oxygen into water is to keep it in motion so that the surface of the water is broken. The towers we use do not need additional oxygenation because the water falls from several feet up into the main reservoir with each on-cycle. All of our other systems have their own air pump and 2-4 air stones. It is the bubble action of the air breaking the surface of the water in the reservoir that gets oxygen into the water - so if you use an air stone, make sure it is strong enough to get bubbles to the surface.

    The pump we use is this model - General Hydroponics Dual Diaphragm Air Pump. They last forever, and if they wear down, you just replace the diaphragm. It is by far the most quiet and is plenty strong enough for the job. We tried other brands and they were way too noisy. You can use a standard air stone and tubing.


    The pumps are not weatherproof, so each has been housed in a plastic storage box (the size of a shoe box). The box is placed upside down and the pump is zip-tied on top of a little piece of foam to the inside of the lid, which is now the floor. Air holes are drilled into the sides for ventilation. The lid and box are zip-tied together. This worked well all winter without letting the pump ever be exposed to or sit in water.

  • Monitoring for pH

    We strive to keep our water between 5.5-6.5 pH. Our untreated water is generally 8-8.5, so we add a pH lowering agent to bring it down. We generally add some whenever we add more water to a reservoir. If we accidentally go lower than this, we will add water to bring it back up, rather than add a pH raising agent. The best lowering agent out there is PH-Down by Advanced Nutrient. It is super concentrated, so only a little bit is needed. In fact it's so concentrated that we never try to hit target in one day, because it is so easy to overdo it and bring the pH down too low. So we add about half what we guess we need and then re-check the next day and add little bit more until getting closer. Use a dropper or small mm measuring cup.

    Filling a 50 gallon reservoir we start with about 50-60mm the first day and adjust from there. Filling a 30 gallon reservoir, about 25mm the first day, and a 20 gallon reservoir, about 15mm. If your starting pH is higher or lower than our 8-8.5, adjust accordingly.

    Once we get the pH where we want it, we generally don't check it again until we add more water or change a reservoir. When we first started doing hydroponics we were measuring and adjusting daily, but you can drive yourself nuts with this, and it doesn't really seem to be that critical - at least not for non-commercial setups like ours.

    There are a lot of inexpensive pH meters out there that will work fine. We ended up going with the more expensive Hanna Instruments Combo meter, as we wanted to test nutrient density as well. If you go this route, buy it from a local store so they can calibrate it for you. Always keep your pH meter in a wetting agent like pH 4.01 so the tip doesn't dry out.

  • Nutrients

    This is a huge market, and we have not tested many brands. If we were growing only one crop, we'd be more exhaustive in our analysis of what was the best for our crop, but because we are growing a large variety of flowers, vegetables and fruit all together, we go with a general nutritional blend. Many people we trusted recommended the brand Botanicare to us, so we've gone with that. We use the GROW formula for our seed tray and when plants are young. As they mature we reduce the ratio of Grow to half and add half BLOOM.


    We are targeting a feeding of 10 ml Grow + 10 ml Bloom to 1 gallon of water.

    We use a TallBoy to filter our water, and the resulting water is generally 900-1000 EC. (We use electrical conductivity rather than PPM to measure density) and strive for a reading around 1900. We measured our baseline water and then calculated what adding 10 ml of each to a gallon gave us (i.e what the delta or difference was). Then extrapolated that to how many gallons of water we were adding to each reservoir. Here is our own chart, which may or may not have relevance to anyone else's setup.

    If you want to keep it easy and not get this techno about it, just change your water more often and add the 10ml per gallon to your fresh new water. If you are topping off your water frequently though, remember that you are also diluting your concentration of nutrients each time.

  • Water Changes

    We generally empty and clean each reservoir every couple months (using that water to water nearby dirt plants of course). We change more frequently if the water just seems a bit gucky or too algae dense or if the plants just aren't looking that good. Since the water here in Santa Barbara is very hard and very chlorinated, we use filtered water (but not RO water, the production of which is too time consuming and water-wasteful for our needs).

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