Changing water

[Shan]

Hi I am new to this list and to the world of aquarium fish. I have a problem and I need some advise. I have a high NO2 level in my tank and am trying to get it down by changing the water. I have so far taken out 30% of the water twice in one day and the NO2 level is still really high.

My question is can changing the water several times a day be dangerous to the fish? Should I be taking out more than 30% at one time ( I have a big tank and it isn't fully stocked yet)?

Please help I feel like I am stuck between a rock and a hard place. I know the water is really bad for the fish with a high NO2, but I don't want to kill them by stressing them out with water changes.

[Ira]

Hmmm...NO2 is nitrate, right? What do you mean by a really high nitrate level? What PPM? As long as it's under 100 PPM I wouldn't worry hugely, as long as the fish are pretty tough. If it's 50 or under I wouldn't worry. I do up to 50% water changes and the fish don't seem to mind, but I've got pretty nice water.

[Warren]

Is it nitrite (NO2-) or nitrate (NO3-)?

If it is nitrite anything over 0.5ppm is dangerous.

If its nitrate, less the 50ppm is desirable. Anything over 50ppm causes stress on the fishes internal organs. Long term it will cause premature death in most fish.

This is a question that pops up from time to time in most forums. Everyone says just do water changes until it comes right. I suggest you look for the cause of the problem.

How long has it been a problem?

How old is the tank?

How old and accurate is your test kit?

What ppm is the nitrite and nitrate?

What ppm is the nitrite and nitrate in your tap water?

What happens if you filter tap water in a separate tank?

I had a major problem a long time ago with a high nitrate level. I found that no amount of water changes would lower the ppm. The problem was actually in the tap water. It measured 0ppm on NH4, NO2 and NO3, but the NO3 level stayed high in the tank.

I had about 140ppm NO3. If I did a 90% water change it dropped to approx 15ppm. The next day it was back at 140ppm (or max on the test kit). I set up a seperate tank with a cycled filter and no fish. Guess what, the nitrate level started to rise. One day after a water change the nitrate level was higher than before the water change. The problem turned out to be dissolved organics in the water. These would break down to NH4 to NO2 to NO3, hence the constantly increasing NO3 level.

The initial solution was to do water changes with rain water, but later changed to Reverse Osmosis.

It may not be the water however. If you have an undergravel filter it may just be too dirty. Gravel cleaning is fine, but eventually muck builds up under the filter that causes high nitrate readings. It is quite common to have to strip a tank down that uses UGF to clean out the muck about every 1.5-2 years.

[Shan]

Yes it was nitrite I have the problem with. The chart I use has the level as 4.0 which I think is different to the ppm you referred to. But according to my chart it is as bad as it gets . Thanks for your advice though, it helps a lot. I have only had my tank three weeks so it is still establishing the nitogen cycle. I have just done a 50% water change and will measure the level again in a couple of hours.

If it doesn't get any better I may just have to use rain water or something, there is plenty of it around at the moment I will get there in the end, its just a huge learning process and I haven't found a really good book with all the answers yet. Thank goodness for this web site and others.

[Rob]

If the tank is still establishing then it's possible that the bacteria haven't got up to speed yet. From memory there are two general types of bacteria responsible for the nitrogen cycle in freshwater tanks: nitrosommanas (sp?) and nitrobacter. One is responsible for converting ammonia/ammonium, NH3/NH4(+), to nitrite, NO2(-). Then the second type convert nitrite to nitrate, NO3(-).

During the cycling of a tank you'd expect ammonia to reach a peak and fall away, while the ammonia is falling away the nitrite will reach a peak and then fall away and finally while the nitrite is falling away the nitrate level will build up (and keep rising unless it is removed by water changes).

The reason for the peaks is that initially there are not enough bacteria to process the chemicals, then as the bacteria populations grow they are better able to process the amount of chemicals produced.

Since nitrite is the problem I would guess that you've hit that peak in the cycling scheme and the bacteria haven't had time to multiply to deal with it.

I would continue with the water changes to make sure the nitrite level doesn't get too high, but don't go to extremes - you need to have some nitrite present to encourage the growth of the nitrobacters (convert nitrite to nitrate).

Hope this helps