those goldfish and the pleco are going to be a pain to clean up after. They all have a huge bioload. Cute RES. I have two babies myself right now. They live in a 55 gall on my patio until they are a little bigger.
Aw what a cute little RES. I had one that was a Chinatown purchase but he died ...
You can actually raise the water level when I first bought mine I had him in a 10gallon filled practically all the way to the top with just enough space to get out on his basking spot (same as yours). I also put some soft plastic plants in the tank to give him places to rest on as he swam around. Just make sure non of them can tie him down or you can get some live plants. they're soft were the can't get tangled, they can float on them and eat them at the same time. I forgot which ones are good but a simple search will help you with that.