Originally Posted by OscarFan76
I take water out of dt so I can vac the substrate and then add water back to the sump. If your return pump is on, the water will lower from your sump even though you are pulling it out of the dt.
Taking it out of the dt also has the added benefit of gravity for your vac line.
Top off water goes in the sump as well.
That's if you can pull out an entire wc
without running your return section dry.. I wouldn't advise leaving your return pump on during a water change and as for substrate I don't vac mine at all. Your pumps should keep the majority of the debris off the sand bed and what does come to a rest ill usually "kick up" the debris with my hand or just fan the tank with a circulation pump before/during a DT wc