Questions on my Octo tank?

[SWaquariast]

I have a 20g aquarium with 40lbs live aragonite sand, and 10lbs live rock.

I am goin to put a "Abdopus aculeatus" in this aquarium. For filtration I have a canister filter with the return and intake with exactly drilled holes along with the heater.

My parameters are:
pH:8.0
Nitrate:0.05
Nitrite:0.0
Amonia:0.0

The octo that is at my LFS is very small. Its head is a little bigger that an eraser. They are feeding it very small hermit crabs and snails. Total of 10 a week. My LFS beleives this octo is 2months or less old.

I need opinions on stuff I need and things I need to know.

 

[Echidna09]

Tightly seal the tank and keep it in a critter keeper or other small cage until it's mantle is 1" or so. Cover all intakes with foam. Abdopus should have at least a 29g tank as an adult. Forty pounds of rock is a lot for a 20 gallon and the octopus may feel congested.

 

[SWaquariast]

I have 40lbs sand and only ten puonds of rock. What do you mean cover all intakes in foam. I was going to have all the intakes cover with nylon "breeding net." I would also put a couple larger shells in it and a jar or 2.