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Canadian Fish 10-28-2012 12:21 PM

Nitrates 80 ppm
I typically do a 25% water change on all my tanks once every 8 or 9 days. This keeps my nitrates in all 4 tanks at 5 ppm. Once, in the summer when we were doing a lot of camping, we went 19 days between water changes. One of the tanks was at 20 ppm nitrates because of the delay. Ammonia and nitrites are always zero. (When we kept goldfish, we would occasionally get trace amounts of ammonia in that tank, but we don't keep goldfish anymore)

That's the highest my nitrates ever got, 20 ppm. And just the once.

So I was quite alarmed on Thursday when we tested the water on my 55 gallon Silver Dollar tank and it showed 80 ppm nitrates. It had been a week since the last water change.

Now, I had a peacock eel die this week, and he used to hide regularly. So it's possible he was dead for a day or two before I lifted his hiding place and discovered he was dead. I thought this is why the nitrates were high.

So Friday I did my usual 25% water change. Today I tested the water, and the nitrates are still 80 ppm!
This is quite a jump from the usual 5ppm so I am alarmed.

I have no plants in that aquarium, as it is a silver dollar tank. But even without plants, until now my nitrates have always been consistent.

This is what is in the tank:

4 x Silver Dollars (6")
1 x Hillstream Loach
1 x African Dwarf Frog
5 x Serpae Tetras
4 x Mollies
1 x Leopard Bush Fish (2")
1 x Pearl Gourami (2.5")

TEMPORARY: 5 Bala Sharks (2.5")

A couple of weeks ago we added the 4th Silver Dollar. I can't see how one fish could result in my nitrates being 15 times higher than usual.

So anyway, what should I do? Should I just start doing larger water changes on that tank, like change a third of the water instead of a quarter?

Could this be because I have been feeding blood worms a little more regularly? Could I be over feeding? Would that cause my nitrates to spike?


Byron 10-28-2012 05:06 PM

I assume nitrates are zero in your tap water, but it is wise to test it again just in case; depending where the water comes from, nitrates might come and go.

I would also increase the volume of your water changes; half the tank would be preferable [read my article on water changes here: ].

I would not feed bloodworms more than once, or at most twice, weekly. Not so much for nitrates, but because they are not all that good a food.


Canadian Fish 10-28-2012 05:15 PM

I'll try a 50% change tomorrow, and test the water on Tuesday, thanks.

I don't think my water has nitrates straight out of the tap, some of my tanks show zero nitrates when I test them the same day I do a water change.

I'll use the bloodworms less, I've been using them every two or three days.

Geomancer 10-28-2012 08:51 PM

Do you clean out the substrate during every water change? In planted tanks that isn't necessary (free CO2 and plant nutrients), but in non-planted tanks it's a good idea to get all that waste out.

Another possibility is over feeding. If every piece of food you put in isn't eaten in under 5 minutes I'd cut back.

I agree on 50% changes. I have fully planted tanks and still do 1/3 to 1/2 changes weekly.

Canadian Fish 10-28-2012 09:21 PM

Yeah, I dig right down in the gravel with the vacuum and clean it out.

I think I may have been over feeding a bit. The Silver Dollars are piggies and I've been feeding them more and more lately. I fed them a little less today.

Canadian Fish 10-30-2012 01:45 PM

Well, I did a 50% water change today, and the now the nitrates are 20. Still high. I'm surprised they're not at 40ppm, though, since they were 80 and I changed 50% of the water.

Going to do another change on Friday, hopefully that lowers it even more. From now on, when I do my weekly changes, I will do 50% in that tank.

AbbeysDad 10-31-2012 03:53 AM


Originally Posted by Canadian Fish (Post 1292691)
Well, I did a 50% water change today, and the now the nitrates are 20. Still high. I'm surprised they're not at 40ppm, though, since they were 80 and I changed 50% of the water.

Actually, I'm quite surprised you got a result of 20 so I question the results. My experience (assuming zero nitrates in the source water) has typically been that a 50% water change yields about a 25% drop in nitrates (or so). I think that part of the 'problem' is the color difference between some of the levels such that we're interpreting a result or range rather than getting a specific value. I've had Abbey check results and for example she would say "between 5 and 10" when I might have said 20ppm.

Also, depending on how close the sample is held to the white background of the card. The only true results are yellow (zero nitrates) and deep red (boatload nitrates) ;-)

Canadian Fish 10-31-2012 07:34 AM

Yeah, I thought that was sketchy. I get my testing done at the LFS and usually the same girl does it but this time she wasn't in the second time, and another gave me the 20 reading. So he must interpret it different than she does. After I do the water change Friday,I'll get her to test it. I know she's in Friday morning. I trust her interpretation of the colors over my own.

How big a water change should I do Friday, as I did 50% yesterday? Should I do 50% again?


AbbeysDad 10-31-2012 08:18 AM

You could do another 50% although you may only need to do 25% because of the short interval between the two - but 50% wouldn't hurt.

Is there a reason you rely on the LFS for testing - getting your own would be worth the $20 investment.

Canadian Fish 10-31-2012 08:30 AM

The master kit is closer to $40 here, but it's not the money at all, lol. We spend so much on this crap, what's another $40. But I trust her interpretation of the results over my own. The colors all look the same to me.

We're in there once or twice a week. She checks all 5 of my tanks (used to be 4) every Friday, usually. Last week we went Thursday. She knows which container is which tank, and which fish are in each. This week I had them test the Silver Dollar tank and the 220 on Thursday, Sunday and Tuesday, because of the problem with the nitrates and the other tank is cycling.

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