a distilery of water uses RODI to distil the water. thats basically what hes got.
Hey ive got a 20 g man. you need to try and keep you phosphate and nitrates down. Since you and I both have only 20g of water and 30lbs of rock we cant really add many fish because the chemistry will go haywire!
so here is what you do. get yourself a good amout of those scarlet hermit crabs, like 5-8. snatch up some snails. heck, use 1 snail per gallon. then get into the macros. macro algae are eating up the phosphate and nitrate in my water before the hair algae gets a decent hit at it. I have a clump of chaeto anchored by some rock that does a decent job. It will also house tons of amphipods and copepods that will help in eating detrius. there are some really good looking macro algae out there. looks around and really go for it.
Grass Algae is also pretty cool looking, i just got some tonight.
A few cleaner clams or scallops will also help nitrate reduction.
in effect, you just going to have to starve the hair algae while making the tank cleaner and look better.
also DONT keep you light on for more than 9 hours. i was running them for 12 a day and my hair went UP UP UP..
hope that helps.