As long as the lfs change there filters regularly and they have a DI filter to remove the silicates it will be ok . I just think it's safer to make your own . Nothing wrong with getting it from the fish shop tho . Gha is green hair algae.I have an RO DI mate used it once it would of took a bloody week to fill 25 litres up haha tbh its easier for me just to buy it its only £2.50 for 25 litres of RO or £5.00 for Saltwater what is gha I will get more snails thanks