Lannjo,I'm glad you've decided to stay in the hobby, it's always good to have more people in the hobby! Did you ever find the leak? I'm still puzzled over that, that's the only leak I haven't been able to clearly track down in many years of doing this. I agree that even with the skimmer pumping tank water there are still a few holes in the theory.Calcium deposits take a surprising amount of vinegar to remove, and I advise against using anything stronger like muriatic that is not only hazardous to you, but to equipment many times. At least you won't have any more mushroom corals growing in it waiting to let go and clog a valve. Hazardous to valves, but it was cool to see it in there, I'm always amazed at the places life finds a way. When you do hook it back up you'll probably find that the neck needs cleaning every week or so. A dedicated toilet or bottle brush works pretty well for this (after you pull the cup). It only needs to be clean above the level water sits at (level with the bottom of the valve in your outlet pipe)You might consider PVC shower liner rather than waterproof paint if you have the space. Sold by the foot, available at the usual big box hardware stores.https://www.lowes.com/pd/Oatey-Shower-Pan-Liner-Linear-Foot-Gray-PVC-Shower-Pan-Liner/3127069If you end up removing any of the drywall on the right (standing in front of the display side) of the tank you may want to leave some access there for a magnet. Your powerheads both being on the back works, but some day you may want to move one to the side. I wouldn't open the wall just for that, but if it's open anyways I'd consider it.Remember to calibrate your refractomter before use *every single time*. Sometimes mine goes a month and it stays spot on, other times it moves 0.004 in the same day. I forgot to mention it when I was there, but using the LED light on a cell phone (the one that doubles as a camera flash) actually works really well.I'm not familiar with the lights Chris mentioned, but they definitely sound like they're worth looking in to. If you look around you can probably get a pair of Gen3Pro XR30 Radions used for that price. I sold mine for that price 9 months ago when I upgraded to my current lights. The ReefCentral for sale boards are a good place, unless someone here is looking to upgrade. Just make sure not to mix up the XR15 with the XR30. This of course comes with the risks of used equipment, but your odds are good and you get really nice lighting.I forgot to mention that when I was there, but somewhere around here I have a thread that can be summed up as "If you are new and make a good tank build thread I'll give you a free piece of coral."Also not mentioned, but I would get a small notebook and start writing down your test results. This way when something goes awry there are some clues to start with.As for fish, I'd avoid a mandarin or another wrasse since you have a nice malanurus in there.A single dwarf angel is a 70/30 risk, but something like a flame angel would do nicely if you are willing to accept some nipping.I would stay away from chromis, or add a dozen and accept that you will lose one every now and then.I know I was anti-tang (I'm a card carrying member of the internet tang police), but a yellow or (note, "or", not "and" at this time) tomini may do nicely. Stay away from regals, and personally I think it's too short for a sailfin or desjardini. Add them later on if so, and be aware that you will want to put in nori on a daily basis (I get mine at the Asian grocery)A goby or blenny with a good personality is always a nice touch.Avoid hawkfish as while size appropriate many will eat your CUC.Supposedly you can now get captive bred Banggai cardinals, which is always better than pulling them from the ocean.I would be really careful with damsels (other than the clowns)Royal grammas often do well.