Need Help With an Aquarium Fish Die-Off

I have a 55 gallon brackish water tank in my classroom. The tank is established (18 months now). I use bacterial filtration, in addition to mechanical filters. We change approx 1/4 of the water monthly. The aquarium also has life plants.

The fish are assorted African Cichlids. On Friday of last week, we found the largest fish dead. I removed it and gave it a cursory glance; no ulcers, wounds, signs of ick or dropsy. It was too big to flush, so received a ceremonial burial in the backyard of the school.

After removing the fish, I tested the water for amonnia, nitrites, and nitrates. All in the healthy range. I then did a thirty percent water change, added some aquarium salt, and thought no more of it.

Today I found my second biggest fish dead. Again, nothing wrong with the body that I can see. I've been scouring aquarium websites looking for answers but thought my ATS friends might have a suggestion.

All other fish in the tank are active and appear healthy. We are down to six fish, the largest of which is about five inches long.

Any advice would be greatly appreciated....it's upsetting my students and me.

My first guess would be too much chlorine in the newly added water. Are you using tap water? How long are you letting it sit?

reply to post by AnonymousCitizen


Good question.

I use dechlorinated water from the store, though. So I don't think that's it.

How old are the fish?

have you measured the pH of the water in the tank, and the water that you add? (if those two differ a lot, your fish might get a pH-shock).
The added water, where does it come from? City supply, then it might contain Chlorine, a deep borehole might contain a lot of dissolved nitrogen. You should always let the new water stand for a couple of days so that dissolved gasses can come out of solution.
Have you tested the oxygen content of the water in the tank? simple test, catch a fish and look at the gills, it should be red. If it is brownish or blueish you might have an oxygen problem.

Next time a fish dies, you can dissect it, and look for any abnormalities, like growths on the liver (will tell you if your food supply is too fatty, etc).

Cichlids are normally a hardy fish.

reply to post by nixie_nox


The oldest two (who died) were not quite two years old. The others vary in age from six months to a year and a half. Young for cichlids.

I'm surprised you have plants in that tank. Their native area has little to few plants and seem like every time I deal with that type they destroy the plants. But that aside, what chemicals do you use to treat your water, do you know where your water is coming from, how are you treating the water be for you added it, has there been any other fish deaths, do you have a picture of any of the dead fish, about what size are the fish, how many of them are in the tank, what are the gender of the fish in the tank? Ok I think that should cover the first around of questions. I used to handle exotic animals and fish, so I know how hard it is to get an awnser for you question using the web or over the phone.

Oh forgot one more question, how much light is the tank getting?

Ok really done now.

reply to post by Hellhound604


Ph was normal, both in the tank and in the water I added.

I keep about thirty gallons of dechlorinated, filtered water on hand for water changes. I still add dechlorinator to the water, in a very small dose, just in case.

Are any of the fish secretly carrying machetes? They are african, after all. Seriously though, I would still treat your water with a water conditioner. Is it possible that one of your students has snuck in a pencil lead or other foreign object, just to see the fish feed? Is the top secure and 100%, boys will be boys?

reply to post by ObjectZero


Full spectrum lighting, set on a timer so about twelve hours a day.

They don't bother the plants, but there are only a few in the tank. It is not heavily planted.

Minimal rock substrate, with a gazillion hiding places. I've not seen territorial fights.

When I bought the fish, I just got the "assorted juvenile African cichlids". No way to sex them. However, I currently have two bright orange fish, about four inches long. Two blue with blue stripes (one has horizontal stripes, one vertical). A yellow fish about three inches long. And a plecostamus.

I should have taken a pic of the dead fish. If it happens again, I will. But the bodies did not show any of the typical fish diseases that I'm familiar with. And both had good appetites.

Water temp is set at 76 F.

I use dechlorinated, filtered water from the store. I also add Prime dechlorinator in a reduced amount and Stress Coat for each water change. I change the filters (4) monthly.

reply to post by ezekielken


Possible, but I doubt it. The kids take a lot of pride in the tank.

Off the top of my head, I'd say it's not your water. Since you already said the tank has been running for longer then 18 months. Have you changed the place your getting the water from? Are you getting it from the same sink or what ever that you where be for? Have you tested for heavy metals? The build up would be slower but would result in death still. If you in a newer building the heavy metals would be in the pipe and you could count that out. Any chance for a chemical to get in to the changing water?

reply to post by ObjectZero


I don't see how, but it's a thought.

Has the tank been shifted or moved? This could cause wastes to break loose from the bottom, but you'd see a larger fish death count and cloudy water. So don't think it could be this but I should ask.

reply to post by ObjectZero


No, it's in the same place it's been for the past 18 months.

Thanks for the help, guys. I really do appreciate it.

It could also be a stress death, if the gender count is not right. I think for that breed of fish it was one male to five female, I would have to double check that number to be sure. Also what's the average temp of the tank? It should be around 75F to 82F.

Originally posted by ObjectZero
It could also be a stress death, if the gender count is not right. I think for that breed of fish it was one male to five female, I would have to double check that number to be sure. Also what's the average temp of the tank? It should be around 75F to 82F.

current temp is 76F.

Don't know about the gender, never learned to sex the adults.

Do you know what kind of african cichilid you have? Oscar, Firemouth,Servum, Jack Dempsey, Kenyi, Electric yellow lab, Electric blue or Demasoni. There are a few other but this is the normal range, for me at least.

reply to post by ObjectZero


I have a bumblebee cichlid (yellow with horizontal black stripes). One that is a pale blue shade with a tinge of pink, not sure what it is. Couple of bright orange fish, then a solid yellow.

When I bought the fish, I just bought from the "assorted" tank because they were cheaper. I do know they are all supposedly Africans.

Originally posted by smyleegrl
reply to post by ObjectZero

 

I have a bumblebee cichlid (yellow with horizontal black stripes). One that is a pale blue shade with a tinge of pink, not sure what it is. Couple of bright orange fish, then a solid yellow.

When I bought the fish, I just bought from the "assorted" tank because they were cheaper. I do know they are all supposedly Africans.

The bright orange one I'm betting is a, Red Zebra the yellow one would be the Electric Yellow Lab I listed, the blue one could be a Electric Blue but not sure with the pink tinge or could be another Red Zebra the males come in blue. But sounds like you got all fish from the Malawi Lake area, so that lead away from the water being a problem.
I still think it could be a stress problem bumblebee's can be mean buggers. You don't always find damage on a stressed fish. Where they acting any different be for they died, like not swimming around the tank, staying in a corner, rapid gill movement is a sign as well but it kind of boring having to stare at a fish that long to see and you need to know what your looking for? This would be over a long time, like the course of a week or more.

I also forgot to ask do you have hard or soft water? They do better in hard water.