How’s it going? I’d suggest putting that GSP on an island so it doesn’t start to take over. It also looks awesome once the island is fully covered. I have a piece that’s almost complete.
For fish you could check out blennies and gobies for this size of tank. I believe. Blennies are full of personality, I liked my yellow eyed blenny a lot. Sadly lost it, but am looking to get a Midas blenny next, it’s a good pop of color and not a very common color for small tank fish.