How do you clean previously used aquarium equipment?

I mostly soak mine is a mixture of vinegar and water for a few hours. Then depending on if there is anything dirty, I use a magic eraser with water and scrub it all off (or use those like bathroom toilet brushes to get into the tighter, smaller spots).

If something is toxic about it, depending on what it is I may use a diluted bleach mixture and then soak in water with prime for days. But that’s very, very rare at best.

Plenty of vinegar, tons of those super rough sponges, and dependent on how bad the buildup is, might even need to use a razor blade and a reseal on all pieces of the glass (if using glass) or checking to make sure that the acrylic isn’t flexing too badly anywhere specifically that might cause it to give out.

Vinegar makes it super fast and easy.