Did another water change last night, he's definitely looking improved. Over the next few days I'm upgrading their tank to an Ar620, which will increase the water capacity by at least 50% which will definitely help with water quality, and I've replaced my other tanks tunze 9004 skimmer so I'll put it in this tank (for a total of 2x tunze 9004's!). I just have to finish the hardwood desk I've built for the tank as well as my LED lighting controller.