Algae update: I got rid of all the brown algae. The Otos just went for it and the wood is completely clear of it now. The bits that were on the rock almost all gone now too, although the Otos are less keen on the rock. However I have another type of algae now. Its on the glass. Pic attached. It rubs off but with difficulty. I have to use my fingernail quite hard. It stabilised for a couple of days, but I noticed today it has spread quite a bit. any suggestions on this one? The Otos don't seem interested in this one at all.