what kind of filter sand?

[krap101]

just plain silica sand or zeobest?

and how would you keep the sand inside the filter? (using the diy 5 gallon bucket thingy

[RogerMcAllen]

At the bottom put some floss with some gravel over it. The only problem with sand is that it packs so densly that you cannot move a lot of water through it quickly unless you pressurize it. If you wanted to make a "homemade filter" where water flows into the top and out the bottom, your best bet (in my opinion, not hard fact)would be something like a sponge on top that is removeable, and then fill the bucket with different rocks/gravels starting wtih the biggest on top.