gravel vac and sand.. how does it work?

[deeni0z]

Since sand is pretty lightweight compared to gravel, how can you do water changes and aggravate the substrate in order to get all the gunk out of the substrate? Won't the sand get sucked up with the water?

[shawmutt]

With sand, all the gunk generally stays on top. Holding the siphon a few inches above the sand sucks up all the gunk but leaves the sand. It takes some getting used to, but that's how we do it.

[TankGirl]

Exactly. After the tank is mature the sand tends not to drift around much, and the mulm just sits right on top. The suction draws all the gunk off. I then usually give the sand a stir from time to time to keep it aerated.

[deeni0z]

Ohh! Thank you so much Shawmutt and TG!!

[Voodoo Chilli]

It is important to stir the sand from time to time: anaerobic air pockets can form in the sand and cause serious trouble when they do escape. My [acronym:fa990452fd="Malaysian Trumpet Snails or Multiple Tank Syndrome, depending on context"]MTS[/acronym:fa990452fd] do a great job keeping the sand in my tanks aerated, but I still gently sift it a couple times a month, just to be on the safe side.