Water changes - what is "normal"?

[sparkyjf]

Hi there,

I've been keeping tropical fish for the best part of 5 years now with a variety of results, mostly successful but some really sad/bad times too. I'm considering a change of setup for various reasons and I wanted to get some advice from the community before I do anything.

For most of the time I have had my tanks, I have been changing water on a weekly basis. I have tried testing the water quality at the end of each week and the results have been fairly consistent across the years - ammonia and nitrite levels are low, but nitrate levels are off the top of the chart that my test kit will display (solution turns the darkest possible red on the colour scale).

I wanted to ask - is this "normal"? I know that water changes should ideally be done in response to the health of the tank, levels of nitrogen compounds and so on, however is it normal to need to change the water (often around 50%) on a weekly basis. Does everyone else do this, or do people achieve consistently longer intervals?

My fear is that although this has been my "normal", I might be doing something wrong, either with my cycle setup and stability, or my filter setup, or something I haven't even thought of yet.

All comments and advice gratefully received.

Thanks in advance!

James

 

[fluttermoth]

Welcome to the forum, James

High nitrate is a symptom of overstocking and/or inadequate water changes. You will need to reduce it gradually, or your fish might get shocked, as they will be used the the higher levels now, even though it's not good for their long term health.

If you give us some more details of your tank, we can help you pinpoint the root of the issue.

However, I consider 50% weekly water changes normal, as do many other experienced aquarists, including many of the members here; all my tanks get that as a standard.

 

[Demeter32]

I do 50% weekly water changes on all but my fry tanks in which I do them more frequently. If your nitrates won't go down it is one of three things, an over stocked tank, too few/small water changes, or you could have nitrates in your water source.

 

[Colin_T]

Hi and welcome to the forum

I recommend 75% water changes and gravel cleaning the substrate each week. However, my own tanks got an 80-90% water change and gravel clean each week.

If a 50% water change is not diluting the nitrate enough then do a 75% each week. If that is not enough then do it twice weekly. Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

 

[seangee]

I do 60-70% every week, irrespective of my test readings.

 

[NickAu]

I do 75% every week, and often 2 times a week.

 

[FishGuest5123]

A lot also depends on what you have stocked. For instance, my goldfish produce much more waste than my tiny neons. If my goldie tanks are 40 ppm by week end, I’m a happy camper. If my neons were at 40 ppm, I would freak! Of course, I do weekly w/c and gravel vacs anyway and partial w/c mid-week.

 

[Cichlid4life]

Hi there,

I've been keeping tropical fish for the best part of 5 years now with a variety of results, mostly successful but some really sad/bad times too. I'm considering a change of setup for various reasons and I wanted to get some advice from the community before I do anything.

For most of the time I have had my tanks, I have been changing water on a weekly basis. I have tried testing the water quality at the end of each week and the results have been fairly consistent across the years - ammonia and nitrite levels are low, but nitrate levels are off the top of the chart that my test kit will display (solution turns the darkest possible red on the colour scale).

I wanted to ask - is this "normal"? I know that water changes should ideally be done in response to the health of the tank, levels of nitrogen compounds and so on, however is it normal to need to change the water (often around 50%) on a weekly basis. Does everyone else do this, or do people achieve consistently longer intervals?

My fear is that although this has been my "normal", I might be doing something wrong, either with my cycle setup and stability, or my filter setup, or something I haven't even thought of yet.

All comments and advice gratefully received.

Thanks in advance!

James

if your nitrates are that high, how come your fish aren't dead? what kind of test kit are you using? teststrips are not accurate and liquid test always are if you follow the directions.

 

[seangee]

What is your nitrate reading out of the tap? Its worth checking. Mine is 50 ppm and for years I did everything to avoid it ever going higher. The fish all "appeared" fine but I suspect their life expectancy was reduced. For the last year or so I have been actively reducing nitrates before adding the water to my tank. Of course its much too early to tell the long term effect on my fish - but I feel better for doing it.

 

[Byron]

I agree with all other members that have suggested significant partial water changes, regardless. I do somewhere around 60-75% of the tank volume once each week.

The aim of these water changes is to achieve and maintain stability. The pH and nitrate are the two best tests to do regularly, at least until an obvious stable pattern becomes clear. Nitrate prior to a water change should never be higher than it was at any time previous, including after the last water change. And the pH should also be steady, within a couple decimal points, from week to week or test to test. It might vary a bit right after the water change, that is normal and not a concern provided it is not a significant change.

And as others have suggested, test your source water (tap water) on its own for nitrates. If this is a source of nitrate, there are ways to deal with it; obviously water changes will not remove nitrates if they are coming in with the fresh water. Nitrate occurring within the tank can be kept in check by water changes, substrate and filter cleaning, not overstocking the fish, and not overfeeding.

You want nitrate to remain below 20 ppm maximum, and as low as possible. My tyanks run in the 0 to 5 ppm range, and have for many years; I only do spot tests every couple of months now because I know they are stable, and nitrate and pH never varies. The water changes are a major reason, along with proper stocking--which involves not just numbers or size of fish, but compatibility of the species.

In post #1 you say ammonia and nitrite are "low," what exactly is the test number? These should be zero.

 

[Colin_T]

if your nitrates are that high, how come your fish aren't dead?

Fish can tolerate nitrate levels over 100ppm but it is not good for them. I have tested other people's tank water that had over 120ppm nitrate and the fish had been in that for a couple of years. It's preferred not to let it get anywhere near that high but fish can tolerate pretty high levels.

For optimum fish health try to keep nitrates at 0, however that is very difficult to do and normally keeping nitrates below 20ppm is recommended.

 

[Phil Fish]

Wow I thought 25% water changes and gravel vac a week was the norm! I am now going to do 50%.

Thanks!

 

[Colin_T]

Big water changes are not just to remove nitrates. They also dilute the microscopic organisms that live in the water and remove fish waste and general gunk from the tank.

 

[FishGuest5123]

A lot of people only change 25% a week and believe you risk cycle issues if you do anymore. I don’t see how on an established tank. On another forum I hear this quite often. However, I agree with Colin_T that it’s better to do a larger one, at least 50% to 75%.

 

[Rtessy]

Personally, I think you have to balance nitrates and kH. Do a water change if nitrates are over 20 (not possible for those wirh nitrate in the water though) or do a water change when kH drops to avoid a pH swing. I normally do 10% a month for my tanks, but they're essentially filterless still ponds, except for the goldfish one, lol.