Thanks.even if you only need 1 get 2. When it gets algae covered, you can put int he second and take your time cleaning the first. and just rotate them.
i use the magic eraser on it. works great.
The bum moved to the left and a bit lower. No way to get it without disturbing all the rock. Now only stinging GSP, no biggy. Will see if it starts bothering my cabbage.