Hello, my aquarium is growing algae which I believe is cyano. I went six months without doing a water change because I have been remodeling another room in my house. I know algae generally grows because of phosphates in the water column/rocks/sand but it looks like cyano can grow from poor water flow. I currently am running one koralia #3 and one number #4. I use to run another #4 but I got tired of the constant sand storm so I removed it about two months ago.
Last week I did a 15 gallon water change and tried to suck up as much slime as I could but I wasn't able to get it all before I had to stop. This week I did a ten gallon water change and continued sucking up as much as I can but still feel like there is a little in the sand in areas I can't reach. The 29 gallon sump has two soccer ball pieces of rock that don't have a speck of algae on them which confuses me because I don't run much flow through the sump. I guess the rock may not have algae growing in it because it is unlit.
I run GFO (last two years) because my previous attempts at growing cheato have failed. I know some people will say cut back on your feeding but I barely feed my two clowns and my watchman goby. I have had the aquarium setup for close to three years and I used new sugar sized sand made by caribsea when I orginally setup my aquarium. My sand ranges in depth somewhere between and inch and an inch in a half, I've never vacuumed the sand because I've always had a cleanup crew and a goby.
I've been considering removing all the sand on one side of the aquarium and adding some Caribsea - seafloor special grade reef sand in hopes I can kick up the flow a little and still keep the goby and the cleanup crew. My thought is after I remove the sand I can replace it with the new sand and then wait a couple of weeks and do the other side of the aquarium in hopes I won't start a cycle. The reason I am considering this is because I hate the sugar sized sand and I sure it's sucked up some phosphates over the years.
Ok I know there are multiple run-on sentences and no real questions but I need some feedback on my random thoughts of what I should do to better my aquarium. Sorry for the edit it may help if I add pictures.