Water Changes

[gregzz4]

Do you know what your total system volume is ?
10% per week is a good starting point to see how things go

Lets say for argument's sake that your 250g holds 200g after rocks sand overflows etc, and your 70g sump holds 50g after baffles etc
So, for my arguement, we'll say your total system volume is 250g
You could do 25g WCs per week and all is good ...

If you can, try to figure out what your total system holds
It's good to know this, especially if you need to dose stuff