Backyard Aquaponics
A place to discuss aquaponics

I am glad to have found you. With the covid shut down I took on a project I have wanted to try for years. I set up my 40 gallon fish tank to water lettuce. The plan is to grow a little lettuce year round in the house. I read a little online and ordered a couple of books that I have not read yet. April 29 I had all the parts built and things were going great until today when half my fish died The water looked clean, no algae growth, the PH was 7.5, temp was 75F, Everything seemed normal. But it wasn't obviously. SO I did a quick 3/4 water change and will tomorrow as well to save the other fish.

I am guessing the plants were too small to filter out the fish poo and turn it to fertilizer. But I do not know. The other thing is that the clay balls started growing white crystals a few days ago. What is that? Did that kill the fish?

My set up, (more of a failing science experiment, like in school.) Is a 40 gallon fresh water tropical fish thank, with 3 angelfish, 2 graumis, 3 platys, 1 molly, 3 swordtails. 2 algae eaters. (now just angels, graumis, and algae eaters. ) The tank still has it's filter running since the system is new and the bacteria had not grown yet, and an airstone bubbler.

A pump circulates water to a pipe across the top of the top grow bed. It drips out on both sides of each plant that was sprouted in rockwool squares. That water then runs down small hoses on each side of the plants in the next growbed below. From there the water flows back into the fish tank. This happens for 15 minutes every hour.

The lettuce is growing and the fish were fine yesterday. It lasted only 2 weeks. I have obviously missed something . Help, please.

(I do not know how to change the order of the photos. And the 10 gallon tank in the photo is not part of the system)

Sorry to hear about the fish. The white stuff on the clay balls is various types of salt that form deposits as the water evaporates. It's not that unusual to have some on the media like that especially if the water is coming out near the surface.

Tough to say what caused this. Usually when you get a fish die off like this it's because of something like shock (from changes to their system or transport), water temp, oxygen, ammonia or nitrite. Since you mentioned that your filter is new then that makes me think it's probably that you had an ammonia spike or nitrite issue. The plants mostly use Nitrates - these aren't particularly toxic to the fish so lack of plants isn't likely to be the issue. Bacteria take care of the nitrites and ammonia. Your existing aquarium filter, if it was cycled should be doing this. If you did have a spike of either ammonia or nitrite then it's possible that the other fish won't make it either because they may already have had too much damage - there may not be much you can do to prevent this. I would increase the aeration and add about 1 part per thousand of NaCl (sodium chloride without iodine or anti caking agents). This will help the fish with stress and nitrite toxicity.

I would also check the temperature during the sunniest part of the day to see if there is a lot of heat gain in the aquarium - I doubt it but just in case.

Think about what changed before the fish die off and you might find the likely cause.

+1 to what Scotty says. Sorry about the fish. Probably ammonia or nitrite, this is very common for a new system that has not cycled yet. It's helpful to have a test kit, something like the API Pondmaster, so you can monitor the water and adjust as needed.

Also, I can testify first hand that the salt helps protect the fish from nitrite poisoning. It doesn't help with ammonia though, and toxic ammonia varies with water temp and pH. I don't recommend table salt - too many additives. But aquarium salt, pool salt, or water softener salt (like Solar salt) that is free of any additives will work, but it must be chloride salt (like NaCl or KCl). Water is 8.34 lbs / gallon, so take your water volume (40 gal) x 8.34 x .001 to get the WEIGHT (.33 lbs x 16 = 5.3 oz.) of salt to add. DONOT add directly to the tank. Dissolve in water first.

The salt also helps discourage certain parasites and pathogens.

Thank you both. I was thinking ammonia issue but had hoped the carbon in the filter bag would take care of that until the bacteria got up to speed in the clay balls. Then last night I had a brain flash. I did not examine the dead fish too closely because I was in a hurry to get the water changed. But I did notice one big orange one had it's belly eaten and a few bites off one of the blue platys. One of the swordtails was pregnant. I did not remove her because the 10 gallon has baby red platys in it right now. I figured the sword babies would feed the angelfish in the big tank, so I did not worry about her. My Black angel is a devil. He has eaten fish before. But usually it is in the middle of the night and only one. If she started to give birth it may have triggered him into causing a feeding frenzy. Maybe that is what killed them so fast. He is a pain! And maybe not. All the aggressive fish survived the night but still show stress gunk on their fins. So I may loose them too. If I do I'm replacing them with mellow fish.

Tomorrow morning I will make the hour drive to Twin Falls to try to find a test kit for ammonia and nitrates. Hope I can find a store open in the shut down. Is the NaCl (sodium chloride without iodine or anti caking agents) something I should also be able to find at the pet store?

I just checked the angels and they are acting fine but do have fin issues. I want to take them out of the big tank and medicate them for a few days in a smaller tank, less medicine needed.

Should I just keep using the same water for the plants after I take the fish out? Or should I add some nutrients to the water. I have a bottle of FloraMicro 5-0-1 that I have not tried yet. It is made by General Hydroponics. If I put this in the fishless tank for a few days and then clean the tank real well before I put the fish back in the tank next week some time, would the FloraMicro wash out of the rocks and hurt the fish in the future?

When You refer to cycling, does that mean when the bacteria have established themselves in the clay balls? How long does that normally take?

My question is where you bought your fish and how long ago.... i was supplied a heap of different fish for free off a wholesaler and about 2 weeks later this also happened to me... i put it down to bad stock... as i have had mollys platies etc for many many years and personally after checking everything was ok put it down to weak stock....... but with yours you hadn't overstocked... salts are excessive if buildup like that..are you leaving water sit for a day before putting it in your tank or straight from the tap..?

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Not good having angelfish with anything else they will eat everything especially any little babies

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I agree, Angels are not my favorite. But I inherited them from my grandson years ago. He always comes in and says hi to "His" fish. Ugh! Two of the fish casualties were also a couple years old in my tank. The rest of the dead were a month in my tank. I will get a test kit tomorrow, hopefully, and find out if the water was the culprit or the angel fish. It just happened so fast.

It sounds like you may have narrowed it down to an ammonia issue.

But, since they were fine in your other tank, and this possibility crossed my mind, I have to ask: did you use any silicone on your AP components? If you did, and it happened to have any mold or mildew resistant additives, it could possibly kill your fish.

Evaporation concentrates the salts and leaves these deposits. It's better if the system water doesn't evaporate at the surface of the media like this because the buildup can cause problems for the plants. I would probably lower the water level in the grow beds to keep the moisture level below the surface.