I have had sallys for 3 years and never lost a fish to them yet. Maybe I am lucky,and it would only take once and they would be gone. Sone of mine have gotted quite large too.
I would think that your 20k would give you all the blue you would need.I would try the white for a year, then when you replace the bulbs go with something else if not happy.
I have had my yellow leather for almost two years now. I got it at a frag swap for $15. It had two heads on it and both are doing great.Iam crowding them too much at the moment with other leathers.
I put one tablespoon of vinegar per gal of kalk water.I usually do this 5 out of 7 times.I have had no trouble with this,have been doing it for 3 years.
You can fun carbon,just change weekly as it starts putting things back into the water once it gets saturated.Carbon also helps when you have mixed corals,soft and sps for example. I use a small bag and use it passively,( not in power filter).
Most people will tell you to stay away from canister filters ,unless you are only going to run carbon in them . The mediums turn into nitrate factories..