Backyard Aquaponics
A place to discuss aquaponics

I started my IBC aquaponics system last year with 14 hybrid catfish. I'm located in South Texas so I thought that these were fish that I could grow all year without a heater. At first they did great. My system cycled quickly and I only lost 2 fish. Things went well for several months. I had a crazy huge cherry tomato plant, kale, lettuce, broccoli, radishes, parsley. I was experimenting and all seemed to be fine. My pH runs high, 8.2 but other than that no problems.

Along came cooler weather in December. When it got down in the 40's at night, I began losing fish. One every few days until finally by February, I was fishless.

I decided that it might be better if I not try to raise edible fish in a plastic tank, so I purchased 35 comet goldfish and 7 four inch Koi. Right away the goldfish started dying. The fish store told me that losing half of them is expected, that's why the are 29 cents apiece. In a few days I was down to one goldfish but all of my koi survived.

After all the goldfish died, the koi are now dying at a rate of one per day. I've checked my water chemistry and the only thing problematic is the 8.2 pH. The fish hatchery had said this should not be real problem, the pH runs higher in this part of the country anyway.

I keep adding rain water to they system and have not made up with any municipal water in months. My media is expanded shale that I bought from a person big into aquaponics who said it should work, but did tend to raise the pH a bit, but not enough to hurt anything.

I have some muratic acid and have thought of trying to lower the pH a bit, but am afraid to do so. I've read that it's hard to maintain a constant pH and swings would be bad.

I'm sorry this is so long, but I haven't asked for help in a long time. Anyone out there have any suggestions for a frustrated newby?

I thought of trying tilipia but didn't want to deal with a heater. My system is in the open on our back patio.

Water temp and key measurements?

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My guess is that you might have daily temperature swings. Cooling off at night and heating up during the day.

Can you post some pictures of the system, sometimes they'll tell us something that the other parts don't.

Topups into the system, are you using straight tap water? Treating it? Filter?

An IBC sized system shouldn't be too bad with daily swings, smaller yes, but an IBC should be fine, and goldies are pretty good with temp swings.

When the fish die, do they look completely normal? Flared gills? Sores on the body? Sunken stomach?

And what are you feeding them?

I'm topping off with rain water. Have not added any tap water in months. I haven't checked the thermometer in the water, but the air temperature is in the mid 70's F at night and mid 80's F during the day.

I'll have to run an analysis to post all results, and I'm at work now. When I checked 2 days ago, the nitrates, nitrites, ammonia were all very low. The pH is running 8.0 to 8.2 the best that I can read the color.

Last night I tested my expanded shale media with vinegar and there were continual very fine bubbles coming off the media. I'm thinking that is the cause of my pH issues. I'm trying to not spend too much money on this system. If I try to adjust the pH, what is the best method? I have some muratic acid but have been afraid to try. I don't know how much to add. With the current water level, I have about 175 gallons of water.

I'm attaching a couple of pics of my system taken last fall when my catfish were still alive. (sorry, I couldn't get them to rotate.) I have a bell siphon in the center of my grow bed that is firing well. My water flowrate may be a little high. The siphon fires every 5 minutes or so.

Suggestions are welcomed. I'm thinking of trying to adjust the pH, add some tilapia and see if they live.

By the way, the dead goldfish looked like some of their scales had been disturbed. I thought that perhaps one of the Koi was a bit aggressive and was killing them. Now that the Koi are dying, they look ok, no ruffled scales, just dead. I have two Koi left as of yesterday evening. Both were swimming around looking healthy this morning when I left home.

Sorry to hear about your fish MarilynH.

For adjusting the pH see the first paragraph of my post at the bottom of this page - http://www.backyardaquaponics.com/forum/viewtopic.php?f=12&t=27187&start=15
If the media is causing the pH to be high then adjusting it may not be practical. Try a test where you put some of the media in a bucket with system water and see what it takes to adjust the pH down to what you want. Let it stand like this until the pH stops drifting and see if the pH drifts back up where it was (you might want to mix it occasionally). If it does you might want to repeat the adjustment - if it goes back a second time, you're probably not going to be able to do much adjusting to your system water.

Even with the relatively high pH you'll still do fine but you'll have to use either use chelated iron or spray apply the iron.

For your fish -
Have you added any salt to this system? Adding 1ppt of uniodized salt without any anti-caking agents helps the fish with stress and nitrites. Having fish die one or two at a time like this over a period of weeks is often seen when you have had a nitrite spike. The salt is cheap insurance and only affects strawberry plants at this level.

Toxins are another thing that comes to mind - What type of roof is the rain water coming off of, what is it made from and what are the gutters made from, storage container?

Algae growth? Some algae can be toxic and even those that aren't can deplete the oxygen overnight to the point that fish will die.

Hope something here helps

How are you collecting the rainwater? If it's from a tar shingled roof, then they may be leaching very bad stuff into the water. I see your IBC is brown, you didn't paint the inside, correct? Paint can leach harmful chemicals too.

Thank you, scotty435 and thorn for your thoughts. I didn't even think of salting the system. I did this last fall when things were working well. Duh!! I will definitely try this again. Much of the rain water is falling directly on the grow bed, but I am collecting some from roof runoff and the shingles are composition type, so this could be part of the problem. The roof is 13 years old, so I didn't think it would leach much, but this could be a contributing factor to the fish problems.

My system is painted on the outside only to protect from the South Texas sun and photo-degrading. I used a couple of coats of black and a brown topcoat so it would blend with our home.

There is a very thin film of green algae on the inside wall of the tank. There were some small red worms growing in the algae but the gold fish got rid of them the first day in the tank and greatly reduced the algae as well.

I will look into adjusting the pH and see if that helps.

Scotty, you mentioned using chelated iron. Is that to help the plants since the pH is high? How do you add the iron? You mentioned spraying it. How is this done?

I wanted to try to add more fish this weekend but will not have time for a couple of weeks. There are still two live Koi and they were very active tonight. I'm hoping they will be survivors. I will try salting tomorrow to see if that helps.

Again, thank you!!!

Iron is locked out when pH is high. You can foliar spray it to get the plants to absorb it. I did that my first year when my pH was in the same range as yours.

Agree that adjusting pH can be tough if your media is buffering and that it might be better to let it be.

You look like you had great growth. Wondering if your beds might have some dead zones where it is impacting water quality.



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Sounds like algae is not the problem and neither is the paint. Right now I think the roof runoff is the most likely culprit but I'd certainly try to prevent this whether it's what's causing this problem or not. The metal components, like downspouts and gutters might also be part of the problem since fish can be sensitive to low levels of dissolved metals like zinc or copper. If you've been getting rain water off the roof and it's held in a barrel for later use (which I doubt), you could have it tested for metals at a water chemistry lab (it might not be worth it, check the cost first it might be expensive). You might have a county or state lab that will do this free or inexpensively (extension agents might know about this sort of thing).

Spraying the iron on is pretty straight forward. You'll probably find the amount needed per gallon of water on the instructions that come with whatever product you have and just put the mixture in a sprayer to apply. Spray on the plants well, usually to the point where drips fall off the leaves. Maxicrop plus iron will work for this or Iron chelate. Fe-DTPA is the most commonly used around here because it can work at a higher pH (if you're using it in the system water) and doesn't affect the color of the water like Fe-EDDHA does. I'd still spray the chelated iron but it gives you some options depending on the pH (your's might be a bit high even for the DTPA iron chelate - so definitely spray it on).