Hi, don't know if you know this already, and I have posted this before, but it bears repeating as it may help stave off potential disaster, if not for you, possibly for another reader with similar problems:
http
/www.aquariumfish.com/aquariumfish/d...788&search=
... Probably the biggest repository of helpful bacteria in your aquarium occurs on the surface of each piece of gravel. Each grain, though appearing smooth to the eye, is rough at a microscopic level, and thus provides a huge surface area for the growth of helpful bacteria. So, it follows that if you sterilize your gravel, you will destroy most of the biofiltration in your tank. Not knowing this, hobbyists sometimes remove the gravel for cleaning and have been known to boil it, scald it or (worst of all) use bleach or soap to sterilize the gravel. This is a huge mistake! It kills off the nitrifying bacteria and will allow ammonia levels to increase rapidly in the water. Gravel should never be cleaned with anything but plain, aquarium-temperature water. ...
It's better, if avoidable, not to remove gravel for cleaning.
If you do have cyanobacteria, (blue-green algae) in slimy sheets throughout your substrate, however, and do not wish to use an antibiotic like Maracyn to kill it off, you may have to, but at least you'll know that doing this may cause spikes you'll be on the watch for, fully prepared to do as many additional water changes as necessary to protect your fish while the nitrifying bacteria re-establishes throughout your tank.