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

[Jeff S]

I don't have any recent pics. The ones I have on this site are real old. The GH was 8x10, now it's 8x32. I also have 3 small systems in my basement, mainly because I' m not smart enough to combine them. I think it's just keeping myself busy. You picked the right hobby for fun and engineering. There's no limit to what you can create in aquaponics. For a few years I had to try everything I saw on YouTube. I went from not being interested in gardening to IBC aquaponics, worm farm(found out aquaponics is a great worm farm), Raised beds(5- 16 footers), 3 compost bins, and the list goes on. I have really overextended myself. Now that I mentioned it I think my next project is going to be consolidate my basement systems LOL.

[Kurt Fischer]

Yes that sounds like it would keep you busy, I am planning to add some verirmiculture ,but since I don't have media beds it will be a separate unit. What kind of fish are you currently raising?

[Jeff S]

I'm raising Tilapia here in Michigan. It's a struggle to keep the water warm. 1000 watt bucket heater and a water coil from my wood heater but only works when I burn wood. What kind of fish are you using?

[Kurt Fischer]

About 120 bluegill, 6yellow bulkhead, 1 tench, 3 goldfish and a partraidge in a pear tree,ha ha.

All caught last Oct in a minnow trap in lake Champlain. It took 3 weeks to train them to eat the Ziegler finish silver 3mm food, at first I had to grind it and moistened it gradually getting Niger and dry . Now most are big enough to eat it whole and dry . The yellow cats and blue Gilson have put on a couple inches.

I plan to start with some blue tilapia  in March after I get my 50 gal. Aquarium set up to start and breed them in.

I wanted to go through 1 winter to see if my design was up to maintaining 70f water all winter and even at 14 below with 32 below wind chill and just a 4500 way water heater element it held 70 in the tanks. So it should work .

So you advocate a pH of 6.5 how do the tilapia like that or is it just in the breever tank that they like 8 ish.?

Do you have blue or Nile ?

[Jeff S]

I have Blues. I keep the water at 66 in the winter. Not interested in breeding or fast growth so that's how I get away with the temp.  I could make it warmer but I'm already spending about $70 a month on electricity just to heat the tank. My system is a total of about 500 gallons. The 6.5ph is a compromise between fish and plants. Fish don't seem to mind. 

Looks like you're stocking density is maxed out. Don't do what I did and overstock. You'll wind up chasing your tail trying to keep the solid waste at bay. Although I'm still overstocked I recommend understocking so you can better balance your waste and plant nutrients. You can always feed fish more if you need more nitrates. Tilapia produce 300-600 fry when they breed so be careful not to get caught up in too many fish. I give away fish to anyone in the area that is interested in getting started in aquaponics. Don't get caught up in "special" fish food. I feed mine wild pond fish food I get from a local big box store at about $13 for 40lbs.

[Kurt Fischer]

Thanks for the excellent advice , if we were closer I would ask to see your setup.

my system is about 1700 gallons total and I built the 2  500 gal. Fish tanks to be self cleaning.

they have V bottoms ( pic during build below ) with spray manifolds at both ends that keep a gentle flow across the bottom to a center pickup that collects about 5 % of the water flow depositing all the poop ( a technical term) into a radial flow seperator with a cone bottom that I made out of a plastic barrel. So I just drain the solids 1 a week and airate in a separate pail, let settle and add the suppernaut back to the sys.

after the water goes through the grow tanks it gets pumped through a fluidized sand bed with 100 lbs of pool filter sand and falls back to the fish

 I built a automatic feeder that feeds the fish 3 x a day so I don't have to be there at a special time each day. Nitrates steady at 40 ppm, will need to thin fish as they get bigger.

Anyway, I agree with you on low stocking density. I only have 115 sqft of grow tanks so I would easily overload with nitrates even with a moderate density. I can shoot a video showing all the mechanics of the sys . And post a link if you're interested.

best, Kurt  oh ya sorry about the typos in my last post , I really should proof after writing.

[Jeff S]

You obviously did your homework before you started. Problem is you've done all the right stuff upnfront so you're going to miss out on the re-engineering part of this hobby LOL. I took the other route and tried to build on the cheap using IBCs and various tanks. Would have been a lot easier to just buy what I needed up front but then I'd have missed all the "fun". You've re-cycled your entire system but in a much bigger way. If I could do it all again it would be a lot different for sure. But I like taking on new little projects and adding to my system. My latest endeavor was adding a barrel to the top of my wood heater to capture more of the heat. Problem with that was I did it during this last polar vortex and was down for the coldest day. Fortunately all went well and was only down for a day. Major improvement.

I'd be interested in seeing your system details. I'll work on getting some pics too.

[Jeff S]

Just a side note, the V bottom in your tank is cool but my IBC tank bottom stays pretty clean too. Everyone says a round tank is better to circulate solids but my rectangular tank works fine. Might be that it's overstocked and the fish keep the solids moving around so they don't build up. Are you familiar with Bigelow Brook Farms on YouTube. He has just built a new greenhouse setup and has created some cool stuff. Built a geodome before that. 

[Kurt Fischer]

 Your wood burner retrofit was an Excelent idea I have a old 120 gal watertank over my wood fired boiler in my shop it lays horizontal with the inflow near the top and outflow near the bottom, they work great!

I am Guilty as charged on the doing a lot of research,but there was plenty of reengineering and design changes originally I was designing a regular greenhouse/solar building when I first learned about the Aquaponics systems. I did see some of the work at Bigelow brook farms and many others including Friendly Aquaponics in Hawaii and many studies like the u of Virgin  Islands , Arizona and Calgary.

A lot of my design resulted from having a pile of 30' long and 12' long 12" x 4" I beams from the Fire station dictating the size . I also had 3 275 gallon used oil tanks that came out of relatives houses that I wanted to use they went from being the fish tanks , then after seeing the design concept of cornelius drain fish culture tanks goal being not only keeping the bottom clean but also to get the solids out before they get broken into smaller parts , making them harder to remove,but not having room for round tanks I had to get creative to achieve the same result in a different shape. So the oil tanks ended up being the grow tanks.how do you deal with removing solids? How many fish do you have?

Jeff S said:

Just a side note, the V bottom in your tank is cool but my IBC tank bottom stays pretty clean too. Everyone says a round tank is better to circulate solids but my rectangular tank works fine. Might be that it's overstocked and the fish keep the solids moving around so they don't build up. Are you familiar with Bigelow Brook Farms on YouTube. He has just built a new greenhouse setup and has created some cool stuff. Built a geodome before that. 

[Jeff S]

I too try to go with standard length lumber to dictate building size. The less I have to cut the better. My next modification to the heater is to enlarge the water tube in the wood heater to try to get more heat to transfer to the fish tank. I only have a 3'8" line running to the tank coil so I'm thinking if I make the heater line larger I can increase the flow rate and get more heat in the water. That would raise the temp of that 500 gallon mass therefor helping to maintain GH temps.

My last count of fish was around 1200 but that was 3 years ago. I only have a single 65 gallon radial flow filter an I placed polyfiber filters  at the inlet points in the grow beds. I have re wigglers in the beds to eat/break down anything that gets through. I keep the feed rate low to minimize waste. My intention this winter is to harvest most of the fish. I really hate cleaning fish.

These are my Facebook pics.    facebook.com/pg/GardenCityAquaponics/photos     Most are labeled. Make of them what you will. I'm not a big Facebook person.

 

[Kurt Fischer]

Wow that is a lot of fish! How big are the largest?

 Thanks for the link, I checked them out looks like you're making the most of your yard!

is your greenhouse double skin? i saw a video on YouTube about a Greehouse in canada , the guy said he was saving a lot on heat after installing a mylar curtain that hung from cables and was closed at night.

mine has a 2-1/2" thick polyiso panel that gets pulled up to cover the glass at night and stays up on dark cloudy cold days . It uses less kw to light it than heat it with the panel down.

what are the dimensions or your fire box?

Jeff S said:

I too try to go with standard length lumber to dictate building size. The less I have to cut the better. My next modification to the heater is to enlarge the water tube in the wood heater to try to get more heat to transfer to the fish tank. I only have a 3'8" line running to the tank coil so I'm thinking if I make the heater line larger I can increase the flow rate and get more heat in the water. That would raise the temp of that 500 gallon mass therefor helping to maintain GH temps.

My last count of fish was around 1200 but that was 3 years ago. I only have a single 65 gallon radial flow filter an I placed polyfiber filters  at the inlet points in the grow beds. I have re wigglers in the beds to eat/break down anything that gets through. I keep the feed rate low to minimize waste. My intention this winter is to harvest most of the fish. I really hate cleaning fish.

These are my Facebook pics.    facebook.com/pg/GardenCityAquaponics/photos     Most are labeled. Make of them what you will. I'm not a big Facebook person.

 

[Jeff S]

They are all different sizes. Must still be breeding cause there's some smaller ones in the mix. Haven't grown them out in a hurry because of the waste that would be generated. The greenhouse roof is double skinned. The walls are single with 2" foam in the winter, screened in the summer. I put a tarp up in the new 8' section while I was out of town last week and it seemed to block off the section with the wood heater since I wasn't there to burn it for 4 days and allowed the gas heater to work better. I agree with your night cover. We don't get much sun here in he winter so I put up the foam on the sidewalls. 

The wood heater is an old fireplace insert 27" w and 21" deep. The flat top on it made it easy to add the barrel. I should add a pic of that on my Facebook.