Backyard Aquaponics
A place to discuss aquaponics

I'm finding occasional dead or dieing tilapia fingerlings in my FT completely covered in this white clear milky growth. The first time I seen this a couple of month ago I thought it was just the dead fish decaying that had died from the cold temps in the mid to low 50's. I thought nothing of it and was hoping that the up and coming warmer temps would help alot.

However yesterday I found this little guy barely hanging on to his life with a mild case of this growth all over it's body. Some of the dead ones were completely cocooned in this stuff. So I obviously have a more serious problem that needs attention, but I'm not sure what to do. My water parameters have been steady and never been toxic levels IMO:

Steady Readings over the last couple months.
PH=7-8
Ammonia=0.25
Nitrite=0
Nitrate=2.5
Temperature=58º - 69º "Currently 62º"

Has anyone ever seen this and how to fix it?
I have a 400 Gal system, about 25 tilapia this size or smaller, 7 - 6" Bluegill, 6 - 6" Channel Cats, couple of comet feeder gold fish. The Tilapia and goldies are the only fish that had died in my system. The cats are hiding somewhere at the bottom I can't see them. The Bluegill have been the most active up until lately have not been eating as well.

Any idea's on what I should do?

I am no expert on fish ailments so take this for what it's worth. If you have never noticed this on a live fish it's probably the bacteria that is attracted to a dead fish. This can happen really fast. The cause of the death is probably something else... Cold temps, rapid ph changes ect.

Thanks aboman, I know its a little cold for tilapia but the PH has been steady. The last one I found yesterday in the photo was still alive when I pulled it out of the water. It was motionless in the water and flopped around a bit when I pulled it out.

Hmmm... In my reading there are some fungal infections that cause thick slime to develop on fish but I don't have any first hand experience with that.

Have you salted?

Yeah I read about that fungal and bacterial possibility today too. I hope whatever it is I can accurately diagnose it so I can properly treat it. @skeggley No I haven't ever salted before. Is that something I could safely try?


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Just a FYI if someone can diagnose this. Notice in the two photos when the fish is submerged the white fuzzy stuff kind of floats around. When it's out of the water it kind of lays down like wet hair. It's slimy but it's not slime because it's attached to the body like really fine hair. It doesn't rub off either. Strange.


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Yes I think you should salt to 2ppm I believe is recommended. Higher than that and some plants may suffer but if the primary concern is the fish then you probably should do 3ppm.

I don't know how to measure ppm, is there a per gallon measurement for approximately 400 gallons?

Oops I should have said ppt (parts per thousand)... Anyway, I have never had to salt mine before but the calculation I have seen goes something like

3g per liter
3.78 liters per gal so 11.34g per gal.
If you were going to treat 400 gal to 3ppt that would be 4536g or 10lbs of salt.

Hope this helps.

Sounds like it's too late for your fishy little friends but always having a ppt salt level is IMO a good idea especially when bringing outside influences like fish and (sigh) pet shop water.
If they were my fish I would salt my ft to 1-2 ppt and put them in a hospital bath at 10ppt for 10 minutes once or twice a day until they showed signs of improving or died...
I foolishly took fish with similar symptoms from someone who, incidentally, didn't feel the need to salt and all survived except one which was dispatched when no improvement was seen in a month.

My tank water is really dark red because I added some EDDHA Chelated Iron and I can not see the fish unless they are at the surface which doesn't happen too often. So yesterday I started blind scooping and caught some of the other fish in the tank to check on them and they all look as healthy as can be. No signs of this growth or any other illness on the Tilapia bluegill or goldfish. I was unable to catch any of the catfish, so I guess they are healthy too if they can swim fast enough to get away from my net. I'm going to salt as a precautionary measure and keep an eye on it. Hopefully it will sort itself out and I won't have any more dead fish.

I agree. Salt.

Actually this conversation got me thinking about adding salt (never had too before). I have had no fish issues to speak of but I do have some new fingerlings in my tank that did not seem very hungry or active so I thought I would salt to 1 ppt just to see if there was any change.

I salted last night and this morning those fingerlings seem markedly happier. Their eating well and in the mix with my larger fish.

Good luck!

I have been having this problem lately, I just started my system about three weeks ago. I was so eager that I didn't cycle my system at all; just throw in 40 medium size gold fish into a 600 liter system.

So far I have had 5 fish die which is 10%, and the last two have died withing the last three days. I have noticed a lot of white lumps of something that looks like pus. Also have noticed clear signs of fin rot.

I have an outdoor system with temperature changes in the water from 14 C to 25 C daily, and my pH has been hovering at around 8.5. I have not added any salt to the system because aquarium salt is not available in my area, and I am not sure what other type of salt I can use.

I am really worried that I will lose all my fish.

If anyone can help me, I would really appreciate it.

It would be helpful to know the following:
1. What is the length, width and depth of your grow bed(s)?
2. What is your ammonia and nitrite levels?

In the absence of this information I would recommend salting to 3ppt as described above.