Cucumber in the aquarium how deep of a sand bed do you need
 

i was thinking of picking one up to help keep my LS cleaner,but my ls is less than 1cm deep ,is this enough and what kinds are the best i dont really care what it looks like the black ones are fine,its how they fair in the aquarium ,any thoughts ?:)

Tiger tails are good but I'm not sure how deep the sand needs to be.

I don't think a sand bed of that depth coupled with the footprint of a 20 gallon tank would be optimal conditions for a cuke. I'd skip out.

I have a black cucumber and the damn thing never sifts the sand. I always find him on the glass in a fast flow area, and I've had him for about a year now.

I don't think a cuke is necessary in a 20g. You can get small conchs but they will grow. Some do grow quite fast but you won't have a problem selling them in the buy/sell forum after they've gotten too big.