Websites are great for opinion but poor for facts. Put your faith in books written by scientists and industry experts.
"There is a similar range for acceptable salinity, but it is a narrow band, around 35 to 36 parts per thousand (ppt). At normal reef temperatures temperatures, this is a specific gravity of about 1.025 - 1.026."
p15 Marine Invertebrates by Ronald L. Shimek, PH. D. 2004
This must be the light?
http://www.aquaticlife.com/products/286#1 I don't think I've ever seen 18" HO T5 bulbs for sale before. Does Big Als sell replacement bulbs in their store? I don't see them on their site. The recommended replacement schedule for T5s is up to every 6 months I believe. I personally don't follow that with my own fixture but I'm sure some people do.
Is your 20gal only 20" long?