ive started looking into liners for the grow beds. im looking to have grow beds that are 4x50x16''. the liners are expensive though. is there a cheaper alternative or is this something i have to just bite the bullet and do? is there some sort of sealant i can coat the gb with? any help on this would be great. thanks for the input.

ive done some research and watch a bunch of youtube videos on it. i am starting a farm. i was going to go with traditional farming but after looking into aquaponics, it seems stupid to do anything else. im on a very tight budget so im having to think outside the box so to speak. ive got 2 swimming pools coming. 1718 gal each. not sure if i should make both fish tanks or use one as a sump. looking for good ideas for grow beds as well. any help would be great. thanks