Algae under sand

TrashmanTodd · 12-01-2002, 12:00 PM

Hey All,
My sand is starting to get green about a 1/2 inch down. The top is staying fine plenty of guys to help keep it clean. I'm wondering what I can do to take care of the algae or should I just leave it.

Todd

wetmanNY · 12-01-2002, 8:53 PM

Is if really a black color rather than green? My hunch is that it's photosynthesizing anaerobic bacteria. Could be cyanobacteria though. Sounds like you very wisely don't disturb your substrate. Black tape over the area would discourage all of the photosynthesizing bacteria, or you could neatly paint out the substrate with black acrylic paint on the outside of the glass.

You have the start of a Winogradsky column going here! Cut-and-paste " Winogradsky-column " at www.google.com and do a search. Your substrate probably isn't rich enough in organics or deep enough to start hydrogen sulfide production, though people always fear that will happen.

RTR · 12-02-2002, 12:05 AM

Just to confuse the issue - is this just at the glass that you see this? And does it appear fairly even over extended distances along the glass, paralleling the sand surface?

If so, a significant part of this may well be only on those sand grains or the glass itself exposed to internally relected light. Light from the tanks lighting entering the glass at certain angles passes through the interior glass surface, but is reflected back from the exterior and comes back out within the tank just below the substrate surface - the glass itself acts a light pipe for a short distance. In one small area, pull back or siphon up the sand, if the algae is still there in the glass with a bit in on the sand removed, it is just internal reflection promoting growth and it may be removed at will. If the patch extends into the tank away from the glass a completely different procees is occuring.

TrashmanTodd · 12-02-2002, 9:31 PM

Hey RTR,
I think yuor right. I didn't notice before, but the algae is only growing in the places with the most light. So, I will cover they area and I think that will take care of it.
Todd