playsand???

yep

Beware of your ph, if your tap ph is low, you'll need a cichlid mix or some substrate that will raise the ph for certain cichlid species. Sand is neutral.
I think ther are some geophagus that need a gravel mix to sift through. They pick up gravel in their mouths sift thru it for food bits and spit it out.
So, sand wouldn't work well I think.


EDIT: I found this. Interesting.


Geophagus steindachneri is easy to keep, but it does demand good water conditions. This fish frequently stirs the substrate which can put a lot of waste in the water column. I performed regular partial water changes of 40-50% of the tank volume.

Since this fish "chews" the substrate looking for food, provide a fine, soft material. I recommend a sand substrate for this fish, but it can be bred over standard gravel or even in a bare bottom tank.

Pool filter sand is cheaper, and of more consistent and a bit coarser grain size. You get it at hot tub supply stores. :Angel:

The playsand works great, as far as pH goes, baking soda and epsom salt will take care of your pH and gH probs.

Geberal Rule of thumb I believe is 1 pound per gallon, I would say 60-80 pounds of sand would be good for a 55 gallon.

Bowes

1 pound per gallon, but I recently did a gravel to sand change and used closer to 80 pounds. but it all depends on how much sand you actually want in there and how high you want it off the bottom of the tank, like if you want to still be able to see the bottom of the tank.