About a month ago I did a gravel vac and tbh my tank was somewhat bad full of alage but I scraped and cleaned up the tank walls but when I gravel vacced lots of green was under the sand causing a very dark tint of green to the water. It was so bad I couldn’t see an inch in. 3 weeks later 5 10g at a time water changes and it’s 50% better. I’ve used both pristine and clarity with no luck