Phosphate

[Jayne]

I have just purchased a second tank, with all the contents live rock skimmer, ect, it has not been very well cared for, So I have started to try and improve things, it is a 200gallon tank, it also has live sand. The tank was running TWO external filters which were absoulty filthy,I have taken one off completely, removed and replaced some of the media in the other, the plan is to remove the external completley, but i am not brave enough to do it in one go I have done two quite large water changes, The magnesium was almost non existant so I have now managed to get it to 1350ppm, the other problem i have is the phosphate level is sky high I have rowaphos in the external, 100g how long will it take to reduce before i need to replace it?

[Sarmo]

i'm sure that someone smarter than me could answer that question but i would just test the phosphate every two days until is quits going down and then replace the rowaphos with a new batch.
Is there anything live in this tank? if not, have you thought about taking it apart and scrubbing the live rock clean and siphoning the sand/gravel. then start fresh with all new water? that may be cheaper in the long run. do you use RO/DI for water changes?

good luck!