A glass hydrometer has given pretty accurate results for me when I test it against my refractometer. You can get a refract online for about $70.
If you plan on adding bigger fish, then shoot for the 30gal. If you acquire smaller fish, or juveniles, then the 20 will do. QT is usually used for 1 fish at time, unless you have a mated pair or a small school you want to add. My QT is a 20L, but I'm pretty much stocking smaller reef fish. You don't really have to have overhead lighting, but it helps to an extent so you can look at the fish more closely to check for health/disease. I like the Eclipse Hood, and I've now also added one of Fluval's underwater PH's which also is equipped with a media compartment. The Eclipse hood is pretty convenient because it has the filters and lighting, but it doesn't give much room for expanding equipment options on the QT.
You're right, I have said stuff over and over, which is why, after many member requests, I went thru the trouble to write up a very detailed info sheet on QT. I’m not employed by SWF.com, I’m a volunteer moderator. I work full-time, and, in addition, I spend about 10+ hrs here trying to help SWF.com members out, particularly in the Disease Forum. When members tell me they don’t have time to do research, my response is, then don’t take up this hobby. The marine aquaria hobby is not like collecting stamps, where you can put it aside when you don’t have time. We deal with live animals and living ecosystems that require daily care. Most of my spare time is spent on this hobby, reading and researching being no small part of what I do, or what any serious hobbyists needs to do. I’m not saying you have to spend your whole life taking care of your fish tank, but if you don’t have time to research or if you aren’t available all week to do some “quality” time with your tank and live pets, then perhaps you should reconsider getting in to this hobby at this point.
