Drain recovery tank? Do you mean the sump tank?
You could make a tank with liner and some framing (but beware of termites.) or you could use a stock tank.
I have 4 more barrels left to use
You could turn some barrels into your sump tank.
It would have tobe lower than my beds correct ...I have 4 beds now what amount of water am I looking at 100gals .???
If you are going to flood and drain your media beds, then yes the top of the sump tank has to be lower than the bottom of the media beds.
I talk about sump tank sizing in this blog post
I will look for it. .I tested the drains all work good (They drain) happy with that now for the sump pump set up .
Ok I just read it and if I have 100 gal volume 4 50 gal barrels cut in half .I would need About a 60 tank ?
Yep, minimum 60 gallons, you could always go larger to allow yourself room for expansion.