[reeferious]

simplest(cheapest) to somewhat messy
1 baited small narrownecked soda bottle sunk to tank bottom
2 baited widenecked bottle with oil funnel jammed against opening (wideneck
enables shrimps to easily crawl inside through funnel but heck trying to
crawl back out.
3 be a shrimp fisherman. crazyglue a size 20-24 triplehook onto end of
plastic rod and simply snag shrimps out. (you might or might not want to
bait hook first.
4 buy a pest trap from lfs
5 add shrimp eating fish to your tank