As a newbie, having returned to the hobby after 20 years or so, I am a little confused with what I have been reading and would appreciate advice on my set up. I got rid of an attack of hair algae about a month ago by daily water changes and dosing with Flourish Excel. However, the hair algae has started to return, so I must be doing something wrong. Below are notes of my current set up and procedures;- Aquaone UFO 550 Tank - 70 litres Aquagrit substrate (recommended by LFS for good plant growth) UFO lighting PL - 11w 8000K White x 2 units Light on 9 hours per day 1100 - 1400 hrs & 1600 - 2200 hrs Daily dose of 1.8 ml Flourish Excel & 1.8 ml Tropica Plant Nutrition Running two chambers of Nutrafin Natural plant yeast CO2 system, 10 day cycles each chamber, alternating recharging between chambers with new yeast every 5 days. (Reluctant to have pressurised system in my lounge) Have been changing 20 litres water weekly -is this too often? (water treated with Nutrafin Aquaplus conditioner) & also weekly treating with 10ml Stress Zyme for biological filter. Tap water is 7.6 pH . Tap water after 7 days is 7.3pH (drop checker still pale blue) Ammonia, nitrite and nitrate readings are all 0 4 pearl danios, 5 harlequins, 4 ottos & small peppermint plec Fairly well planted tank but hair algae threatening on amazon swords & crypts. Vallis does not grow well. New leaves on crypts appear weak and distorted. Any advice would be appreciated!