Chaeto and gracillaria stopped growing for me because I use GFO. Right around the time I took this picture is when it happened, I was using 1 cup each month. You can see that some of the strands are pink because coraline algae is growing on them. Beneath the surface there was nearly as much sponge as algae growth within this ball. I ended up giving most of it away and the little bit that I kept disappeared shortly after.
