Repeating death mystery - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 6 Old 12-31-2018, 10:29 AM Thread Starter
Post Repeating death mystery

Newer 75gal tank, fully cycled. (reads 0 ammonia, 0 nitrites, ~10 nitrates) pH stable at 7.4, weekly 30-40% water changes and large pothos plant growing out of tank. Water has been tested on 4 different types of kits. 95% of the fish I have tried in this tank has died. I've tried numerous cichlids and now switched to feeder goldfish as I don't want to be throwing more money out. Everyone acts okay for the first few days then one by one they die off. Symptoms can either seem like swim bladder disorder or the fish (more often) suddenly starts hanging at the bottom or top and dies within a few hrs. My congo tetras look great so does the pictus catfish. They've been in there since the begining. I thought it could be the decor, so I took out all the driftwood and rocks. Curently in tank -black sand by caribsea, brand new fake plants. Temp is currently at 74F for goldfish, was 77F for cichlids. I have a 500 aquaclear and the 450 hydor canister, both with original media. Anyone have an issue with this sand? Maybe there was a toxin from the old rocks/wood that's now in the filter? No sign of disease and I'm positive it's not water quality otherwise.
The goldfish were very lively the first two days, now none will eat and they are very inactive. Two have died of the seven (they're about two in, I will move them to the pond when they grow more). I feed an algae sinking pellet and general flake. Nothing filled with wheat and fillers.
Thanks, this has been heartbreaking

Last edited by Genos; 12-31-2018 at 10:34 AM.
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post #2 of 6 Old 01-06-2019, 10:25 AM
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Have been thinking about this. Had a similar experience. Instead of black sand had black gravel.
Took out all of the offending stuff and replaced with natural river rock. I would like to add that it was the first time that black gravel was used. Then I added a common pleco and waited. The die off stopped...
I don't why, but the presence of the common pleco helped balance the tank. Also want to add it is not the first time I have used the common pleco to stop a die off after making sure water changes were done. Filter rinsed in salt water etc.
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post #3 of 6 Old 01-06-2019, 09:05 PM Thread Starter
Turns out the sand I used from caribsea was no longer sold by them due to toxic levels of heavy mental in it. Took the sand out and everything is good. I'm not sure how a pleco would help correct a tank imblance...
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post #4 of 6 Old 01-09-2019, 11:24 PM
This is a little off topic but it reminded me of my water analysis tonight. I haven't lost a single fish for weeks so I have been lazy about testing the water. I have around 25 or 30 fish in a 36 gallon tank. Even the last school of cardinal tetras survived and I think neon tetras have been over-bred to death. Anyway, I found my pH was 6.4 when it is normally 7.0. Ammonia was 1.0 ppm where it's normally zero. Nitrates were 80 ppm and they are normally much lower. I'll do a big water change tomorrow but there was a time that I would have thought these conditions were going to kill my fish. Life is strange. They all look just fine. Serpae, cardinal. black tetras, multiple colors of mollies, corys and all.
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post #5 of 6 Old 01-28-2019, 09:11 PM
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Sounds like you may be overstocked. Would probably account for your water parameters. I had about the same number in my 75 and felt like it was overstocked although most are 2to4 inch size and a few in the 4 to 6 inch.
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post #6 of 6 Old 01-29-2019, 08:43 AM Thread Starter
This has been solved by removing the contaminated substate. It's not overstocked
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