Aquaponic Gardening

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Hi All-

I'm a newbie setting up a raft system in a 20x24 greenhouse. We've got a 300 gallon tank with 128 sf of grow beds. I know when I fill it the pH will be off the charts. We live in western Colorado and are high alkaline here. 

We have a well with good water that we soften through a potassium chloride system. Should I add chlorine at the initial fill just in case? (We've been drinking this water for years and have had 'Extensive' testing done due to the gas drilling out here.) Should I bypass the softener when filling? 

Can I add pH Down that I use in my hot tub to help bring the reading down? 

We've had aquariums over the years but this is something new and I'm a bit nervous - don't want to kill my fishies or plants right at the start!! 

I'll be having lots of questions so thanks for the help!!! 


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Replies to This Discussion

First of all, welcome to aquaponics, Darlene!

The answers to your questions are influenced by the type of fish you'll be raising, because PH senitivity varies with species.

We live in AZ where the water is rock hard and PH is off the charts. We're raising Nile Tilapia, which are pretty PH hardy. Unfortunately the plants like the lower PH so we still have to work to get it to the right levels. We use peat moss stuffed in old nylons, and just float it in the water. This has brought the PH down to the low- to mid-7s in our outdoor tanks. Everything seems to be doing OK at this level, so we're happy!

For our indoor breeding tanks we use RO water, which has an extremely low PH level, mixed with regular water to get the right balance, because the breeding fish prefer really low PH.

The chemicals for regular aquariums should be avoided because, unlike your hot tub and regular aquariums, you probably plan on eating plant and possibly fish. Chlorine can be used to clean the water, but it can kill fish and plants, so if chlorinate, make certain you age it to allow the chlorine to dissipate before putting it in your system.

As for the salt from the softener, again it depends on the type of fish you'll be using and how much salt is in the water after softening. If you've used the soft water for aquariums and house plants with no ill effects, you'll probably be fine. You can test it with one or two fish in a small tank or a bucket for a week and see how it goes. Be sure to have a bubbler going, though.

You'll benefit from having had aquariums in the past, because you've had to experience the nitrification process. If your fish can tolerate the current PH levels, don't worry about PH until your system has cycled. The cycling process is more than enough to worry about! :)


If your water is safe for you to drink, I wouldn't chlorinate it!!!!!!!!  It would just be an extra step and expense that could really slow the process of cycling if you were to overdo it.


As to the softener.  Well, I don't think you should use softened water all the time for your system but the potassium chloride might not be bad thing on occasion.  Heck, many of us add sodium chloride to our systems to help mitigate the effects of nitrite toxicity and it is actually the chloride ion that helps in that situation.  So while I can't really guarantee that using your softened water is safe because I don't know the exact details of your system or what else might be added to the potassium chloride pellets, I doubt that using the softened water to top up occasionally will be a problem.  Using your well water to top up all the time may cause you issues with too much calcium and too high a pH and iron lock out so perhaps alternating back and forth might be a good option for keeping pH up yet still getting the potassium you will need.


Some people recommend using RO water or rain water and I've been switching some of my systems over to rain water since my well water is hard too.


If you must adjust pH of water using acid, I can see doing it with a system pre fish/cycling and then in the future once fish are in, you need a separate barrel or something to do the pH adjustment and let it stabilize before adding to your system to avoid pH bouncing hurting your fish, bacteria and plants.

Thanks for great advice. We're planning on setting up barrels for rainwater catchment so that should help when we have to top off. And good to know about the chlorine - didn't really want to have to if not absolutely necessary. Getting really excited as we get closer to filling and cycling.


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