your tank looks excellent and I love moors, but I have to tell you as someone that has kept fancy goldfish for 6+ years, that little guy is going to quickly outgrow that tank. Goldfish need a min. of 10g per fish to really thrive and grow - they poop A LOT! So you may want to think about setting up at least a 10g in the future as he grows. Not trying to burst your bubble, but I have gone through A LOT of goldfish and they need a lot more care than people think. In fact a black moor was how I got started in this hobby. I got one in a mini shelf tank and it quickly developed Ick, after researching why it got sick I got involved on a message board and started in this fantastic hobby. If you have any questions or want to further discuss goldfish please feel free to bug me anytime! Good luck! It is a nice looking scape you have.
Ya I have had black moors in the past also, so I know about how much they poop. But I haven't had outgrowing problems in the past, but it might be because I just had them for a year or so at a time. Oddly enough the first black moor I ever had got ick also, so thats kinda funny.
. But he lived through it luckily.