Cyanobacteria typically appear as blue-green to black bubble trapping sheets. Like other chlorophyll-bearing creatures they utilize light (though not a lot), CO2, and dissolved organics. This is where you can beat them. Create a hostile environent by increasing the oxygen level in the water (surface agitation or a simple increase in flowrate in their area) and by taking the dissolved organic compounds (DOCs) out of the picture via fractionation (skimming) or precipitation (kalking). The reason they hug rocks and substrate is proximity to the waste products of the fauna hiding within.
Sometimes red sometime clear Dinoflagellate sheets are a slightly diferent issue. Check your pH (something that gradual kalking can do nicely, thank you). There is plenty of anecdotal evidence that raising pH (and some claim raising temp) suppresses their spread. You can also try to starve them out of nutrients by lowering DOC's.
Both occur naturally even in the most well maintained aquaria, so if they aren't present in alarming quantities...
In an cae, any remedy has to be applied judiciously so as not to stress other tank inhabitants.
I highly recommend physical removal of havy sheets, they can literally suffocate cryptic fauna (and flora) in rocks. Cyanobac and dinoflag alike benefit from the increased nutrients brought about by subsequent tank fouling from all the dead organisms, and we wouldn't want the disgusting, slimey basts TOO happy.