Dark Alage over rock and sand

[gman3000]

Hi

Over the last few months i have had what i am calling alage, very darking colour cover over a couple of rocks and also laying on the sand in places.

Im not sure what it is or why is started to grow, i have to scrape the rocks with something to remove it, when doing this it goes very stringy.

Also I have started vacuming the sand off during water changes about two months ago.

does anybody know what this is and cause?

Many Thanks

[HappyOne]

A picture will help but it sounds like cyanobacteria to me. How old is the tank setup? How often/much water do you change? What water source do you use? Is there strong water flow in your tank (especially where you see this stuff growing)?

[chrisd]

+1

[luther1200]

Coulod be either cyano or dino's. I would look up those 2 to start with.

[Loverotties]

+1

[gman3000]

5 months old
Water change every week 20%
friend mixes water, use ro filter the reef cystals