Cycling My Tank

Hi, I have split this post from where you posted it (in Acronyms Used In Fishkeeping) and started a new thread with it.

Looking at your results, the two of concern are nitrite at 1.0 - this should be zero - and nitrate of 250 - this should be much lower than that.


How often do you do water changes and how much do you change? The only way to get nitrate down is by water changes. It is made by the filter bacteria and there are no bactera that grow in tanks to remove it so the only way to remove nitrate is by water changes.
For a nitrate reading to get that high it suggests your water changes haven't been big enough or large enough - it is usual to change at least 25% of the tank water every week, with bigger water changes needed for heavily stocked tanks.

You need to get your nitrate down by water changes. But with that high a level, other things that we can't test for will also have built up in the water and a big water change would alter the water too much and stress the fish. You need to start off small - 10% every day for a week, then 20% daily until the nitrate level drops to the same as your tap water nitrate.
These water changes will also help get the nitrite level down.

As a rough guide, nitrate should not be allowed to reach the tap water level plus 20, and the highest level will be just before a water change. You need to make sure you do water changes often enough and big enough to keep nitrate below tap level + 20.

Some fish species are very sensitive to high nitrate levels - including rams and dwarf rainbowfish.

There are now thoughts that nitrate levels above 20 ppm do long term damage to fish so you really do need to get yours down. But having said that, the UK (if that's where you live) allows nitrate levels of up to 50 ppm in drinking water, which does make keeping nitrate below 20 ppm difficult in some places.

The problem is that if you go back to what you were changing before, nitrate could well build up again. Once you get it down to tap level, I suggest you test for nitrate half an hour after a water change (to allow the new water to mix thoroughly) then again just before the next water change to see how much nitrate has increased. If it has gone up by more than 20 you need to do a water change big enough to get it back to tap water level.

After a few weeks of testing before and 30 mins after a water change you'll get to know just how much water you need to change to stop nitrate increasing.




The usual causes of increasing nitrate are:
water changes not often enough/big enough
too many fish
feeding too much
excessive use of nitrate containing plant fertiliser.


I don't know if you have any but live plants should also help keep nitrate under control, particularly fast growing stem plants and floating plants.