Source Water For Your Aquaponics: Ag Water and Well Water
Ag water can be ditch water out of a ditch, or water out of a pipe that has come from some sort of an open water distribution system without treatment of any kind. It’s PROBABLY okay to use as is. In reality, it can have anything in it, from deadly bacteria to fish disease vectors, or plant and fish parasites, and you need to be sure you have killed anything that’s in it before you put it into your system. IMPORTANT! How you do this is to fill the system with whatever nasty agricultural water you have, and put in a quart of Clorox for every 600 gallons of system volume to get all that water sterilized. Turn on your pump and your blower, and run the system like that for two or three days, with the RAFTS OFF THE TROUGHS. Every living thing in the system should be dead at the end of the first hour or two. (You don’t want to be downwind from this.)
(Below) Just about anything could have fallen in upstream, or pooped, or died there. This is why we don’t use straight Ag water to fill our aquaponics systems with.
The next two or three days will blow and burn off the chlorine in the system, until you can test it with chlorine test strips and find none. Do the same to any ag water you add to the system later, unless you want some interesting problems to deal with. You MUST USE a makeup water tank separate from the system to dechlorinate any new water, then wait until after it’s tested negative for chlorine, then transfer this safe water to your system, because you CAN’T chlorinate the system again with fish and plants in it without killing it all.
But, can’t I use the clean water out of my nearby stream? Stream water is deceptively clear and sweet smelling. I once drank water out of a clear stream, and then hiked a half-mile upstream to find a huge dead cow floating in a pool. Use the same precautions with stream water as you use with ag water.
Well Water can be extremely clean and pure, or can have heavy metals, toxic agricultural chemicals, and/or chemicals introduced by industrial processes nearby. Because of the wide range of possible contaminants and water quality in wells, it is up to you to determine if your well water is safe for use in your aquaponics system. The best way to do this is to submit a sample to a reputable testing lab and ask for “the works”. Test for everything possible that could be considered a contaminant or toxin. Then decide if you can decontaminate and use it. If you are planning to sell organically certified produce from a commercial scale operation, make certain your organic certification agency will allow use of your well water purified with whatever method you plan to use before you literally buy the farm.
WARNING: Bad Water! If it’s not “city water” or well water that tested clean coming out of the pipe you should treat it as Bad Water and chlorinate it as explained previously. You have no way of knowing and are gambling if you don’t.
If you are planning to sell organically certified produce from a commercial scale operation, also make certain your organic certification agency will allow use of your “Ag” water purified with whatever method you plan to use before you literally buy the farm. Does it sound like you should check out your water source and get it approved before you buy the farm? Yes!
If you don’t mind a little disease in your fish (because none of the fish diseases or parasites transfer to humans or plants) then you don’t have anything to worry about when using agricultural water. Except getting a dose of Roundup or pesticide-laden water in from an unknown source like an irrigation ditch or stream that there was overspray into, and killing all your fish and plants. I know two Hawaii koi farmers who lost their entire ponds full of stock when herbicide-contaminated ditch water came through them. If you’re using ag water, this is a good reason to have a makeup tank; chlorinate the water in the makeup tank, wait until it tests negative for chlorine, THEN put a few sacrifice fish into that tank for a few days to see if there are any herbicides or other poisons in the tank water, BEFORE adding it to your aquaponics systems. If they don’t float after three days, the water’s probably fine.
Testing pH In Your Source Water
We have started systems with water having a pH as high as 8.3 with no seeming ill effects, so don’t worry about it. The pH starts trending downwards immediately as the fish breathe CO2 into the water and it transmutes into carbonic acid, lowering the pH. When the system pH is down around 6.2 or so, add calcium carbonate as mentioned in the section entitled Nutrient and pH Levels, and continue to monitor pH, adding calcium carbonate as necessary to buffer pH and bring it down.
WARNING! Do NOT try to bring down a high pH caused by highly basic water or by having a poorly neutralized concrete tank in your system by using citric acid! Citric acid is an organic herbicide, and will kill your plant’s roots. They all turn black, then the plants all die (courtesy of one of our students whose name we forgot!). We do not yet have a safe and approved method of bringing pH down, just buffering it up with calcium carbonate.