how often do you need to change the water in a fish tank if it uses a filter?

Answer 1

10% a week is rule of thumb

Answer 2

When water evaporates, it tends to leave behind all of the waste products that are generated by the fish. If your filter is really good and you have a heavily planted tank, you would probably be okay with biweekly water changes, but don't think that just because the water is evaporating, it's the same thing as doing a water change! I have a heavily planted tank with a filter, but I still do weekly water changes because I don't want anything to build up too much. My roommate, on the other hand, has a heavily planted 20 gallon that is very understocked (for a long time she only had red cherry shrimp, amano shrimp, and otos in there) and she didn't do a water change on that tank for months and everything was thriving anyway. It really depends on the tank, how good of filter you have, and how stocked you are. If you're at all unsure what to do, I would recommend doing 25% water changes every week and then adding fresh, dechlorinated water. It doesn't take that long to do and your fish will be happier for it!

Answer 3

A filter takes out the particles (food, feces) and some of the chemicals that color the water & makes odors if you use charcoal/carbon. But it can't take out all the compounds dissolved in the water (ammonia, nitrates, phosphates) that can be harmful in high concentrations or will cause algae to grow.

You need to do partial (20-30%) water changes each week to remove these.

http://www.fishlore.com/Maintenance.htm

Answer 4

Generally speaking you can't go wrong with a 25-30% water chance every week. Even the best filter can't remove everything.

Answer 5

I usually change out my water (about 1/3 of the water) once every couple of weeks if it is needed. But most of the time evaporation takes care of it for me and I just add fresh water about once every 2 weeks.
However, at least once every couple months I do vaccuum out the gravel in my tank to remove all of the nasty stuff stuck in the gravel and at the bottom of the tank. I usually change out the water at the same time.
Test your wated if you are unsure if the filter is doing a good job and to make sure all the levels are ok.

Answer 6

If you keep the filter clean, you'll never have to change the water. Water will evaporate over time, as water always does wherever it is, and you'll add more as needed. As time goes by, this has the same overall effect as changing the water, only you don't have to do it all at once. So keep that filter clean!

Answer 7

one fourth to one third weekly... you need to remove the poop, or a nice healthy worm population will develop.

Answer 8

sometimes never if you have a good filter.If you want to be on the safe side once every year ir less.