I keep reading that co2 keeps algae under control. My tanks do not have any injected co2.But, they to receive liquid co2 once when I do a water change and another 3-5 days before another change usually 7-10 days. All tanks are heavy planted and have floating plants. The plants are growing well. Lights are on 7 hours a day. I should do 2 intervals of on 3,off 4 than on 4. One tank has hair algae. the others have some on glass and scraped off when water changed. I read that liquid co2 isn't a substitute for injected co2 but it is good for keeping algae down. What is your opinion?