I have a 40 gallon fish only tank with live sand. It is an established tank (well over a year after moving from another location) seems no matter what I do it becomes over grown with green algae and have had no luck keeping fish healthy other than the damsel which has been in there the whole time.
I have a fluval C4 filter and an eshoops hob
I use RO
filtered water for water changes and topping off the tank.
I change about 20% of the water monthly which seems keep my levels low. My nitrates are typically below 20 and ammonia and nitrites are 0.
my bio load is pretty low as I only have a small blue tang and a blue damsel at the moment. I recently lost a yellow tang which wasn't showing any signs of illness and all were eating well.
I was more concerned about the blue tang as he was showing signs of lateral line disease so I removed the carbon from the filter according to advice given to me by my local shop and then added seachem matrix for added bio filtration.
The only area that I ve been lacking was cleaning the gravel and I am wondering if that is the cause of all my tanks issues. I read that not cleaning the gravel can make an "ammonia bomb" causing fish stress /disease and algae blooms.
So would my best course of action be to change the sand out?
Thanks for any advice
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