The Puffer Forum

See pic

looks like algae & crud buildup
a single edged razor blade should take it off

Is that on the inside? Or are you saying its on the outside of the tank?

I would be concerned if it were on the outside, underside of the tank.

Rotfl the inside XD and I didn't want to stir up the sand if I really don't need to cause it's not very deep... Less than 2 inches

I wouldn't worry about it.

Ok thanks thought maybe I could find something small than would sift through the sand and eat the algae but I don't know if there is anything that would

Just looks like a build up of crud/sediment, probably in the bottom of most tanks

IMHO, 2" of fine sand is a bit thick if not stirred and cleaned routinely. If it has been untouched for more than a few weeks, don't do the whole thing at once, you could release unwanted materials into the water. If that were the case in one of my tanks, I would siphon out ~1/4 inch at a time with at least several days between withdrawals until the sand bed is down to ~1" max. If the bottom of the tank is getting algae from reflected light, cut a piece of corrugated cardboard and pressure fit it in below the tank bottom.

Depending on the grain size of the sand, deep sand beds (DSB) develop strong bacterial layering with depth which can be beneficial to the tank, but only if undisturbed. Unfortunately, you cannot rely on most puffers not to disturb a DSB, which can result in toxins being released in the water. Fish death may result. DSB for most puffers should be in sumps or other accessory tanks.