How to handle Potasium/ Calcium supplimentation when Ph never goes below 7.4

[Richard Kowalski]

Hello Everyone,

This is my 7th year running my Aquaponics system. This is the first time I have run into a problem where the Ph has been hovering between 7.3 - 7.6 for the past 4 weeks. I built a hybrid system that consists  of a 300 gal fish tank. The fish tank has 80 Tilapia fingerlings. The system also has 3 Deep Water Culture  bins where I grow lettuce and 2 grow beds with hydroton growing Bok Choy, Peppers, Cuccumbers, Tomato's, Basil. The entire system is in a hoop house that gets shut down and cleaned out roots and all in the winter because its just too cold and not cost effective to run it year round in New York. The only thing I am doing differently is that this season I have planted alot more plants than I have in previous years because of the amount of Tilapia I am raising. I start all my plants from seeds indoors using Rockwool. There is alot more Rockwool in the system. The first thing I checked for is fish deaths. The fish are fine. The Tomato plants and Cuccumber plants have shown signs of Chlorosis. I tried using a foliar spray of Potasium Carbonate and burned my plants. Luckly I only lost a few of them. I have supplemented Chealated Iron first to see if that would solve the problem. No luck. Thats when I tried foliar spray of Potasium Carbonate.

What have you done to suppliment Potasium , Calcium with such a Ph? Why do you think the Ph is not falling like it should? Water temp is in the low 70's. Its heated. Ammonia and Nitrite is 0 ppm.

Thanks for your time and comments.

Rich K

[Kurt Fischer]

I hear ya on the lack of sun my pv s only gearaned 400 kw in each of the last 3 months as opposed to 1600 for july .Thankfully vts net metering program allows me to use the excess capacity from summer for up to a yr from generation. 

I have built a few add on water heaters, water jackets are best but a few ft of steel pipe can generate some good heat. Do you weld?

[Jeff S]

I can weld but definitely not a welder. I drilled 2 holes in the side of the wood burner and installed a makeshift 3/8" copper tube heat exchange loop inside the heater. I run the water 32' to the fish tank through insulated pex where is goes through a SS coil in the tank. I use a recirculating pump for the transfer. It does work but I think I need to make the heat exchange tube larger so I can transfer more heat. That's 500 gallons of mass I can utilize when I get it right. Plus I can lower my electric bill substantially by not having to just heat the water. The cost isn't really a factor since this is a hobby but seeing how efficiently I can make the system is all part of the fun.

[Kurt Fischer]

Hi Jeff, sounds like you're on the right track . I use ss for the heat exchanger in the fire box for durability,but as long as you aren't going to put it under the logs I guess copper is a lot easier .

 I just shot and uploaded a video to YouTube check the comment under it I will upload part 2 soon talking about the heat exchanger/dehumidifier 

https://youtu.be/CM5tSnI7Qg8

[Kurt Fischer]

So here is the link to the second part about 4 minutes shows the fish and the heat exchanger 

https://youtu.be/Uvlc3dsAfLw