how much water can i change at a time?

[pondboy]

I have a 150 gal tank . about fourteen weeks old .i started off with tap water

. now i have a rodi unit . and want to do some big water changes . i have two marron clowns and about 150 lbs of LR . my levels are ammonia 0.25 nitrite 0 , nitrate20 , ph 8.4 phossphate 0.8 sg 1.022 . I put a whole can of phossphate ban in in my sump a week ago and my phoss are not comming down ?

 

[bang guy]

You can't change more than 100% in my opinion.
I'd recommend a couple of 50% changes, carefully match Salinity and temperature with the old tank water.

 

[pondboy]

so 40 gal a weak shouldn't be a problum

 

[bang guy]

Not at all.

 

[bang guy]

I should add that it's possible your Phosphate has more than one source. If it was from the tap water only I would think it would deplete rapidly as algae consumed it.

 

[jdecter]

Ok heres what I'd do, do a 20 Gallon Change everyday until the water levels are good then maybe 20 every week for a month then, go back to what your normally happy doing. I do about 10% a week.