Nitrate Levels (when it's safe to make a water change)

[Knight~Ryder]

I went and bought a nitrate tester (API brand) and I did exactly as it told me to do. I got a reading of 10ppm.

I thought it would be a lot higher as I have not changed the water in just over 2 weeks. I have been told that it climbs over time and that I should keep it under 40ppm)

So is this telling me that I don't need to do a water change yet? It seems like this reading is very good.

(Side note: Making partial water changes can also help to reduce nitrate, however because many tap water supplies contain nitrate, it can be difficult to lower nitrate levels by this method.)

[JustOneMore20]

Yes and no. You do want to keep nitrates under 40ppm and since yours are only 10ppm, you are good for now. There are other things in the water from the breakdown of waste that you need to get out (and can't test for), so even if your nitrates are 10ppm for months, you wouldn't want to go that long without a water change. Especially if you don't have live plants or anything that takes in the nutrients and such. Even with plants, you need to change water periodically.

I think the best thing to do for the fish is to get a schedule going. Since your nitrates stay pretty low, going a couple weeks without a change is fine. I suggest you try to change about 20% every 2 weeks. Changing water won't hurt anything. Better to be safe than sorry IMO.

[Knight~Ryder]

So if my nitrate levels are low, does this mean my ammonia and nitrite levels should be lower as well?

[JustOneMore20]

In a cycled tank, you shouldn't have ammonia or nitrIte. Ammonia is converted to nitrIte then to nitrAte. Nitrate builds up and the only way to get rid of it is water changes and live plants if you have them. They just keep building and building. Having low nitrates means you haven't had alot of ammonia converted to nitrates.

[emc7]

If you ever think your nitrate is abnormally low, go back and check ammonia and nitrite. They should always be 0. You can test for nitrate in tap water with the same test. Most people don't have that issue, but its important to know if you do.

You have a lot of fish in that tank, but they are all small ones. If you feed lightly and your nitrates take awhile to go up, you can go further between water changes than most people. It really isn't any harder to hold nitrates at 10 or 20 than to hold them at 40. What is important is that you know what you need to do to keep them under control.

[Knight~Ryder]

So maybe I should check nitrates in a week or so again, and see if it went up?

[JustOneMore20]

Thats a good plan. Like I said though, don't go on nitrate readings alone as to whether you should do a water change or not. Get on a good water changing schedule. If you want to see how effective your water changes are by testing a day or so afterwards, that is fine too.