9 replies to this topic

[Fleendar the Magnificent]

I seem to be having a problem with my big tank as I have lost 4 out of 7 spotfin shiners, 2 blunt nosed minnows and a crayfish over the past 2 weeks. My nitrates were quite high in the tank and I have been doing water changes about every 2 days to reduce the nitrates. Other parameters have remained stable with 0 nitrites, 0 chlorine, 0 ammonia and the water being the same hardness, acidity/alkalinity and pH  as they came from originally as I use only source water that they've come from. So far the only fish affected have been the shiners and blunt nose minnows. The darters and N Longear sunfish seem to be fine, active and eating. Any other ideas on what the problem might be? I did a massive water change today replacing 80% of the water I changed 2 days ago with fresh native lake water. Is there something that I am missing here?

 

TIA

Chris M.

[sbtgrfan]

Any symptoms pre-death?

[JasonL]

Chris

I had the same issue in the past, likely caused by overfeeding. Here are my thoughts and what I did.

1. Avoid wholesale water changes for lowering nitrates, maybe 25% per day as more than this can shock/stress the fish further. Unlike ammonia and nitrites, nitrates are a slow killer. No need for more than this per day.
2. I changed out my substrate and rinsed out my canister filter. I think substrate was a major source of my nitrates. I changed from small/medium sized river rock to sand from a local creek mixed with flourite from a LFS.
3. Load up with live plants ASAP, even floating hornwort or duckweed would help. Live plants love nitates and absorb it like a sponge and make fish keeping much easier. Get appropriate substrate. As above, I've used sand and flourite but there are other alternatives.

Good luck. For me shiners were much more sensitive to nitrates than darters. It surprised me, but that was my observation as well..

[Fleendar the Magnificent]

Pre-death symptoms were erratic swimming, nose up, tail down, swim to the bottom and back up to the top nose up to the surface. I think overfeeding plus the nitrates did it as all other parameters were on the green.

 

@Jason,

I tend to agree that the nitrates along with over feeding caused this. I went about 2 weeks without any water changes and the nitrates got high. I did a thorough gravel vac and removed a LOT of mulm and detritus from the substrate. So when I did a change today, the gravel vacced out clean. So I think it was going 2 weeks without a water change, over feeding, and then probably shock when I did a 50% change that caused it. The substrate I have is that natural gravel that is about the size of garden peas and a bit bigger. It's not a fine gravel or sand.

 

Lastly, to me it seems that shiners and some species of minnows are more sensitive to nitrates than others. Perhaps for along the same reasons as gizzard shad. They're just very sensitive to changes, water quality and shock.

 

Chris M.

[Matt DeLaVega]

A heavy gravel vacuuming can also stir up waste and hurt water quality. I don't care for gravel as a substrate. You can sift washed play sand into tank to fill the bulk of the voids within the gravel. Hope this problem is almost in the rear view.

[JasonL]

I had a lot of that detritus you mentioned that collected underneath the larger river rock I had originally. Likely one of the culprits for my high nitrates. Switching to sand and live plants has cut down on my frequency of water changes significantly and I haven't lost any fish in quite a while. Live plants love nitrates and liberal amounts of them are the way to go imo if you can.

[Fleendar the Magnificent]

Thanks for the advice. I'll check on the play sand and live plants. I don't want this happening again. Maybe the craws won't dig as much with sand.

 

Chris M.

[Chasmodes]

Could be the above.  Did the fish seem to gasp for air?  Any signs of disease or deformities?  Are any of the fish "scratching" or rubbing on anything?

[Fleendar the Magnificent]

I noticed before I did all of the water changes that the shiners and bluntnose were spending a lot of time closer to the surface than normal. If I am correct, nitrates lowers atmospheric oxygen absorption into the water, and therefore, breathing harder for the fish. So basically they suffocate.

No diseases or deformities I have seen and they "flash" once in awhile, but not often. I think it's the nitrates suffocating them and then stress from 6 water changes in 3 days. In my experience in the past, shiners seem to be sensitive to shock and change. Might have been just too much.

[Chasmodes]

That makes sense.  The only other thing that I could think of that would do that would be flukes.  If their immune systems are down, which high nitrates can do, they might not be able to fight off gill parasites that might not normally be a problem.