Fish mysteriously dying
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Fish mysteriously dying

This is a discussion on Fish mysteriously dying within the Cyprinids and Atherinids forums, part of the Freshwater and Tropical Fish category; --> Hi, new to the forum, but I can with a decent-sized mystery. I'm taking care of the danios (Danio rerio) in our classroom. I've ...

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Fish mysteriously dying
Old 03-05-2014, 09:19 PM   #1
 
Fish mysteriously dying

Hi, new to the forum, but I can with a decent-sized mystery.

I'm taking care of the danios (Danio rerio) in our classroom. I've got maybe 20 danios in my 20 gallon tank (the professor has previously managed to keep many more with no problem). All of my water chemistry is good, no nitrite, nitrate, or ammonia whatsoever, and my pH is about 7.4, but it is stable. But every day I come in to have lost 3-4 fish in the night. I started with around 40 fish, and I had no die-offs until I cleaned my tank (conditioned and tested the water before adding it) and all of the debris in the rocks got stirred up. That's when they started dying. I have another tank though, with ~40 adult fish (this is for a behavioral study) that are dying too, but I just got them, so they haven't been in their tank for long. I'm feeding them twice daily, but I'm thinking of either reducing the amount, reducing the feedings, or changing the food (any suggestions?).

I just wanted to know if anyone had experience something like this? I'm going to ask my professor if I can spread them out to one of our extra tanks to reduce crowding, but in between now and her reply, and came to look for advice on saving these guys?

Thank you for your consideration of this request.
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Old 03-05-2014, 09:27 PM   #2
 
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Sorry to hear of your troubles. Couple questions before I can offer any possible answers:

Is the tank cycled?
Do you do partial water changes, and if so how often and how much?
Do yu have a heater?
Does the tank produce any nitrate ever?
What filtration do you use for the tank?

Hope everything works out for you.
Good luck!
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Old 03-05-2014, 11:09 PM   #3
 
Thank you for replying. I cycled both tanks several weeks ago (and after water changes) with Nite Out II (Microbe-Lift), and my ammonia levels have held at zero for a good few weeks. I did change one tank a week ago (the debris one), and after which I had a major drop in pH (I'm getting new rock substrate to replace the substrate in both tanks). I have a heater, and I'm keeping both tanks at ~26C. Last week both tanks had a nitrate jump from 0 to 5ppm. I did partial water changes until it absolved itself, and I'm going to test and do another tomorrow. When I do do partials, (once a week since there's so many together) I take maybe 20-50% depending upon the water conditions (more or more often in emergency states). The water in one tank has subtly yellowed, and I was hoping to address it with a water change. But now I'm suspecting the food I'm feeding them (a Tetramin tropical flake, I'll check for the proper label). As far as filtration I use a (large) carbon filter Whisper 30, and the other has a 10-15 that I have to check the brand of in the morning.
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Old 03-05-2014, 11:17 PM   #4
 
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Your methods seem to be sound and your equipment appropriate for the tanks. I'll do a bit of research and reply again tommorrow. Hopfully no more dead fish by then! Nitrate at 5 is nothing that will harm fish. Do you ever see them at the top gasping?
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Old 03-06-2014, 01:27 AM   #5
 
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are you positive that you are doing the nitrate test correctly?are you doing thorough gravel vacs.i would do additional 50% water changes,vac deeply and cut down on feedings until you figure things out.what steps are you taking on filter maintenance and how often?
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Old 03-06-2014, 12:00 PM   #6
 
I've lost at least 3-5 more fish. I tested my water before doing a ~30% change (I'm doing another after my classes let out). In both tanks the nitrate levels have gone up (10-20ppm). My class doesn't have a gravel vacuum, so one has been express ordered (no way to get to a pet store sooner).

But they have been gasping at the top, weaker, and seem to lose the ability to move their caudal fins. Sometimes they just spontaneously drop out of the shoal and gasp at the bottom. They're gills are bight red, and they're red through the scales (I'm not sure if this is normal). Some will bloat up (one, the only I've seen it in) had all of her scales popped out. But I haven't seen it in the others, and they only really seem to bloat at death, but other float and can't right themselves off their backs. This is awful.
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Old 03-06-2014, 12:08 PM   #7
 
I've followed my Api Master kit instructions to the letter and it just never read above zero before now. If I have to (and I probably will) I'll remove the gravel and do a 90% change and save some of the water aside to add back. My professor didn't have a gravel vacuum, so until the one that was express ordered get's here, I can't see a better way than fully rinsing the gravel. I will reduce the amount at feeding, and just do much smaller ones, but I'm afraid to cease entirely because the healthy (still) fish attack the weakened ones if they go without.

I rinse my filters with removed tank water every 3-4 weeks, or if things look bad. I've done a complete replacement of both filters, once, but that was weeks ago. I think it is probably overfeeding, so once I clear the gravel, I hope the fish will recover with reduced feeding.
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Old 03-06-2014, 01:07 PM   #8
 
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can you get your hands on a large sterilite container?match the water temp,dechlorinate,move the heater and filter over.do water changes every other day.add some salt,1 teaspoon/gallon.mix with tank water and slowly add over a few hrs time.from the description,it sounds like bad water conditions.while they are in the new container,clean the tank.remove some gravel if there is a lot of it.clean the rest.leave about 1".when you feel like you have cleaned it well,move the healthier fish,filter etc back.get some tetra safe start and add it to the tank.keep the sickly fish in the sterilite with an air pump/stone combo and heater.keep them on the salt.when you do water changes you will have to replace the salt taken out.make sure the salt has no additives or anti caking compounds.when you feed your fish,do smaller feeding twice daily.feed only what they can eat in a few minutes.if you can watch them eat during feeding time it would help.sprinkle a bit of food in,let them eat it all,sprinkle more in,repeat until the 2 mins is up.watch to see if any of the food hits the bottom.have you considered a few snails to work as a clean up crew?danios only feed at the top.any food falling to the bottom will stay there and foul the tank water.the snails will also let you know if you are overfeeding by populating the tank.if you decide on snails start a new thread about them.the forum members will suggest a few types,and what they can do for your tank.some just eat algae,others eat fish food.you want the right kind for your set up.
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Old 03-06-2014, 08:42 PM   #9
 
I did set up a new tank, and put a few of the fish in. If they all survive, then I'll trust that it's safe enough to add the rest (~5 I added acted strangely, in small ways). I just don't want to push them in one big move like that.
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Old 03-07-2014, 07:48 PM   #10
 
I cleaned both of the tanks, and have treated my fish with aquarium salt. They seem to be doing okay. And if my water chemistry is good in the morning I'll put the hardier ones back in. But I lost one during the salt treatment. I'm worried, because the water got cloudier as I added the salt, but I only added a 3-5 teaspoons (dissolved before adding). Can this hurt them? I left for the night, but I'll be in early to care for them.
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