New small picasso fish? Help?

[yote]

No need to pay those super expensive priced for GFO either. Just toss a box of nails into the bottom of the pool. They will rust eventually and low and behold, you have GFO! For ick, you can just toss in a handful of old pennies.

Should I use galvanized nails or just get the black steel kind? Could those white spots really be Ick?
I was thinking I could put them both in the same pool to save on space. Will one of those sponge filters with the air stone work?