what is this stuff!?

[HovaRockz]

Lol wow you went thru alot... Well it really isn't that hard to get rid of I mean I had alot a while back and all I did was siphon the sand and add flow and in a few day was totally gone...see cyano does not stick to sand or rocks it merely hangs there and is very easy to blow away once a continuous flow is added and I do mean if there isn't a phosphate,nitrate or even iron problem in your tank in a few days u will not see a trace

 

[Reyjgd]

Lol wow you went thru alot... Well it really isn't that hard to get rid of I mean I had alot a while back and all I did was siphon the sand and add flow and in a few day was totally gone...see cyano does not stick to sand or rocks it merely hangs there and is very easy to blow away once a continuous flow is added and I do mean if there isn't a phosphate,nitrate or even iron problem in your tank in a few days u will not see a trace

That's exactly what I did before having to do all that .... The part I missed was that the smart person that tried cleaning it up used a net ... And what the person did was break it down into pieces and burry it under the sand falling into from the net... The only thing that was "clean" were the chunks haha but yea it was a.nightmare water flow plays an important role on the tanks

 

[Gregcoyote]

IMO, selenium can be a cause here. Polysorb, or something like it will reduce selenium levels as well as phosphates. Selenium is found in some types of sand and salt.
But the advice about flow is right on. Cyano only seems to form in low flow areas.

 

[MacDracor]

Selenium? I did not know that. But then, cyano is a strange beast.