Can they be used in a filtered tank? Says they were made for unfiltered ones.

 

I'm not sure, thats part of my concern

 

Ah these are kinda like orbez. Kinda cool. About 15 years ago they had these square gel cubes similar to these for fish tanks so I bought some for my orange betta crush. He used to sleep in them. They eventually broke down into littler pieces and I tossed them and put his gravel back in. He seemed to Honestly like them, scared me one day when it looked like he buried himself in it but he popped right up and out when I walked up to the tank. I didn’t have a filter or a heater back then so I can’t say with any confidence either way about that but I don’t see why it would make a difference unless the filter output spins them into motion. It has beneficial bacteria in it just like we would add to jump start our cycles for our filters. I could see this getting clogged in a hang on back lol