Water change.

[Secondgen]

How much water is recommended to change monthly on a 90 gallon tank with a 20 gallon sump?

 

[TekCat]

not sure about monthly, but 10% of your total volume bi-weekly should be enough in most cases. Besides, it is better, IMO, 2 bi-weekly water changes, than 1 big once a month. ... smaller changes less stress your inhabitants. good luck.

 

[rhenie]

I'd say it depends on your bioload. If you have a bunch of big fish in there and lots of fish poop, then you'll require more changes. Also the age of your tank could make a difference.

We change about 10% a month in our 140G now. More if there's a problem and more often in the beginning.

FWIW

-R

 

[Secondgen]

Thanks for the advise sounds good. I think I will change 30 gallons a month. That should be cool right? If I change 30 gallons once a month instead of 15 gallons every 2 weeks this will be the same as far as replenishment of trace elements right?