Adding more substrate

[Bray84]

Hi I've been using crushed coral as substrate and need to know if can top the tank up with more as have lost good bit from doin water changes.
Will it harm the tank? If ok how to doit?

[Gregcoyote]

No problems with that. Wash the new substrate and lower it a bit at a time in a plastic cup. Don't get in a hurry and stir everything up, just be patient and add it slowly by getting the cup as low as possible so the substrate doesn't fall very far.

[Bray84]

Been told when first set up tank that not to wash the crushed coral as had good bacteria that was needed. Is that a cup at a time or doit all at once

[Gregcoyote]

If its "biologically active" sand, don't wash it. But if it is plain crushed coral, do wash it. Yes, a small cup at a time to keep it all under control.