How often should I be changing my tank water in a 150gallon tank?

6 2-3" Convicts.4 fry convicts.150gallon tank.2 75gallon filters.And a moving bed media filter (that I can't seem to get growing the bacteria).Just figured I'd ask. I'm not having any troubles aside from an algae problem in one of my other questions.But assuming everything is perfectly fine, and I only feed what they eat, how often with my set up?

Once every 2 weeks

With only 6 convicts in that size tank you probably only need to change 10% of the water per week. Changing more will do no harm, but probably isn't necessary.Of course the 4 fry is likely to increase in the future, and you will need to increase the water changes as the number of fish increases.Test the nitrate level as an indicator of water water changes. If the level starts to get up to 30ppm, you need to change more water. There are other pollutants that build up as well, but the nitrate is usually the fastest, so if you control that, the other things will be OK.Ian

1 of my tanks is 200Gallon, I change its water every 6 days, using 15%, My 150Gallon tank, is very heavily planted, so I change the water every 2-3 weeks, but do A 25% water change.