Hippo tangs like to hide in the rocks when sleeping, stressed etc. I've seen tanks with more than one yellow tang. I am not familiar with the cowfish or lionfish. Clowns are pretty easy and with a 220 I'm pretty sure you would be able to have 2 pairs depending on which ones. Live Aquaria is pretty good at listing info for each fish you are considering. They also have a compatibility chart you can use as well. Take your time stocking. It's going to be very hard to go slow, but it will pay off in the long run. This is coming from lessons learned. Quarantine everything in a smaller tank before putting it in your main tank. Ich can cause major headaches if you have to get all your livestock out to treat. It's not fun tearing all your rock work down trying to catch your fish to treat them in a separate tank. Velvet can wipe out all your livestock in a couple days as sometimes the symptoms don't show themselves until it's too late. Ask questions in this forum. This forum has saved my livestock a few times. The people here are incredible. Just remember though that what works for someone else, may not work for you. Every tank is different even if using the same equipment, lighting etc. Good luck and I wish you much success.
