Hi,

I have a 180 gallon tank. I use a 500 gph pump to drain to the desired level (50%) weekly.

I have been doing this now for 4 -5 weeks and NO ILL effects on fish or plants. Quite the contrary actually.

Add PRIME to remaining tank water.

Refill from tap.

Any GH booster should be added at this time.

Please navigate to the Estimative Index on the Forums tab for dosing strategies and amounts.

Hope this helps.

I know other folks do this for larger tanks than mine, so I feel it is pretty safe.