Backyard Aquaponics
A place to discuss aquaponics

Hi everyone, nice to meet you all here.

I have recently bought 5 tilapia fish to my 2 months old aquaponics system which have 3 guppys, 9 silver tip tetra and 2 pelco.

I'm am not sure why the tilapia are dying one by one.

Here are the photo and situations: (i will add in the figures of some

1st Fish - died a week ago



NH4 - 0.50 mg/l
NO2 - low
NO3 - 40-60
KH - 0
GH - 0
pH - 6.0-6.5

2nd Fish – died a few days ago. The night before this fish died, it stayed at the bottom of the tank the whole day.





NH4 - 0.25 mg/l
NO2 - low
NO3 - 60-80
KH - 0
GH - 0
pH - 6.5-7.0

Aeration added a day after fish died

This morning, I noticed that the 2 other tilapia are staying at the bottom of the tank. Yesterday morning. I noticed that one guppy is attacking the tilapia a few times before the tilapia moved away.

Fish 3



Fish 4 - I noticed some spots on the Tilapia. But is unsure what are those.




Also, I've noticed that my kales are wilting at the tip of the leaves. It looks like calcium deficiency but I can't confirm.

Please do share your thoughts.

Pictures of kale added

Always tough to tell what's going on when the fish is already dead but the fish looks like it has a wound that got infected to me (probably bacterial) and from what you describe the guppy could be the cause of the wound. Popeye is pretty obvious but my guess is it's probably just because the fish has been dead awhile.

Your description of the kale sounds like a potassium deficiency but we need more information to be certain. Usually you'll see this sort of thing on older leaves first when it's a potassium deficiency. As it gets worse the leaf margins will die. Potassium deficiency is pretty common in AP systems and I'd try to treat for that - kind of doubt it's calcium but I'm not sure.

Thanks Scotty!

Upon further research, I think my fishes are infected by Hexamita.

1 guppy have nipped tail and curved spine. Also staying at the bottom of the tank.

I can see a white stringy poop floating on the fish tank. All remaining tilapia lay at the bottom of the tank whenever I inspect them.

This is very challenging. I remember all is well before introducing the tilapias into the tank. Could it be the ammonia spike that cause all these problem?

The next course of action would be adding in some magnesium sulphate. No more than 2.5 teaspoons of epsom salts per 10 gallons of water as per the advise from http://www.aboutfishonline.com/articles/dropsy.html

I tried to read up on the neutralization equation but still unsure how much KOH should I add into my fish tank. Do you have any benchmark or literature that I can refer to?

The ammonia spike may or may not have affected the fish - it depends on the pH and temp of the water at the time it occurred and how high the ammonia got. A nitrite spike could also have been the problem. Tilapia are pretty tough fish when it comes to water conditions. If the ammonia was only 0.25 mg/l then it seems very unlikely to have been the problem. I'm not sure about the magnesium sulfate treatment or how you came to the conclusion that this is hexamita (you could be right, I dont' know but it's really tough to do a diagnosis like this based on what you or I know right now ).

If you're at some point planning on eating the Tilapia then use good judgement about what you add when you treat these fish. Magnesium sulfate shouldn't be a problem but keep in mind that magnesium will compete with some of the other nutrients for uptake by the plants.

Have you salted the water to one part per thousand using sodium chloride. This helps the fish with stress and helps them build a slime coat.

What size is this system please? Generally speaking adding fish to an existing community of fish is a risky proposition. The new fish need to go in quarantine for at least 30 days so you can observe them and look for signs of distress. In the quarantine tank new fish are usually treated for parasites and other diseases. Quarantine also gives the fish-keeper a method of diagnosing whether the issue is with the new fish or the fish you already have. Without that information we're really left to guess what is happening.
I hope this helps.
Brian