High Nitrates - Why?

B

Baldrick

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Aug 28, 2006
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Hey all,

I'm still trying to get the hang of all things fishy and am having a bit of a problem.

We've got a 20 gal. freshwater tropical tank with 5 Neons, 2 Peppered Cories, 5 Zebra Danios, a what used to be 2 Dwarf Gouramis (now there's one).

Yesterday, my daughter was very upset that the Powder Blue Gourami was dead on the bottom. I had noticed that the day before it wasn't eating like normal. It also had what looked like red blotches on it's sides near the tail. I didn't think much of it since I'm not very observant about stuff like that and figured they had always been there.

I got home from work today and tested the water with my AP kit. Ammonia was 0, nitrites were 0, but the nitrates were through the roof. At least 80 and maybe 120. It's hard to tell at that level as the colors are so similar.

I quick did a 40-50% water change and will do another very soon.

My question is, is this what killed the Gourami? Also, I do 25% water changes every couple of weeks. Why would the nitrates be so high? My tap water's nitrate level is about 10.

Any help would be appreciated.
 
Did you retest to make sure the nitrates really are that high? How high are they normally when you do a water change? It's likely that nitrates that high may have killed your gourami, but the other fish would probably be affected as well. Have you noticed anything strange with the others?
 
please take what i am about to ask/suggest as an observation and suggestions.

you have a relatively small tank with a moderate to high bioload.(given the tank size)
I would not say you were overstocked.
continue doing small daily water changes..10-20% until the nitrates get to 20.

what kind of filter do you have? do you have gravel? are you doing gravel vac's?

I would bump the water change schedule to 30 % 1xweek.

you could actually be seeing a start to OTS(old tank sysndrome)
there are a multitude of things that occur and some combine and can cause stress..stress in a fish can weaken the fishes ability to fight off infections.
the red blotches were most likely symptom of an infection..

how do you do a water change? I use a python waterchange device..you might want to check in to that. :)

I believe clean water is the single best thing you can do for your fish.
 
debris buildup in the gravel or filter will cause high nitrates, little or no water changes, even the death of the gourami and subsequent decomposotion would have raised nitrates. if you continue on water changes and the nitrates stay low, you have your answer, if for some reason they keep bouncing up then there is another hidden problem somewhere. you should at least get on a 30-50% weekly w.c. schedule anyway, water changes done correctly will not harm your fish.

Who feeds the fish? Not to imply anything, esp. since i don't know how old your daughter is, but if *someone* wanted to feed the fish a little more than usual, that could lead to high nitrates over time.
 
i suspect it was the decomposition of the fish that caused the high nitrate level. while an 80 ppm NO3 level is too high, it will not in and of itself, kill a healthy fish.
 
Thanks all.

Wow, there's a lot of questions in there so I'll touch on the mian ones.

The tank is only three months old. I do gravel vacs with every water change. The Gourami could have only been dead a max of ten hours. Is that really long enough to begin decomposing and change the water chemistry?

I have a Whisper 20 filter on the tank. At some point I'm going to buy a Penguin 150, but the Whisper appears(?) to be adequate for now.

I suspect that we may be overfeeding. We feed two times per day. I give some flake food and try to keep it off of the bottom, but still a bunch inevitably gets past them. I figured that with fairly frequent vacuumings it wouldn't be a problem. I also give a dash or two of bloodworms at every feeding. And for the Cories, I'll drop in an algea pellet or a sinking wafer.

One thing I didn't mention was that I have a fake plant that has cloth-like leaves and it's turning brown like it's rusting. Also, the aligator in the tank is turning brown on it's head. I have very low iron in my water. Any ideas?

Thanks.
 
Baldrick said:
Thanks all.

Wow, there's a lot of questions in there so I'll touch on the mian ones.

The tank is only three months old. I do gravel vacs with every water change. The Gourami could have only been dead a max of ten hours. Is that really long enough to begin decomposing and change the water chemistry?

I have a Whisper 20 filter on the tank. At some point I'm going to buy a Penguin 150, but the Whisper appears(?) to be adequate for now.

I suspect that we may be overfeeding. We feed two times per day. I give some flake food and try to keep it off of the bottom, but still a bunch inevitably gets past them. I figured that with fairly frequent vacuumings it wouldn't be a problem. I also give a dash or two of bloodworms at every feeding. And for the Cories, I'll drop in an algea pellet or a sinking wafer.

One thing I didn't mention was that I have a fake plant that has cloth-like leaves and it's turning brown like it's rusting. Also, the aligator in the tank is turning brown on it's head. I have very low iron in my water. Any ideas?

Thanks.
Click to expand...

The brown is most likely brown algae. It is a diatom that is very common in newly set-up tanks. It feeds off of phosphates and silicates. It should wipe of easily, except on the silk plants where it can get in between the weaves of the cloth. Eventually it will all stop growing.

Cut your feedings down to 1 per day, don't worry too much about underfeeding, you could feed every 2 days and the fish would be just fine.
 
Whispers are HOBs
 
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