They were never as good as early literature suggested. By that was mostly dead spots and not enough flow. Reverse flow and later powerhead versions changed this, they worked pretty good. What killed them I think is Fluvan made Eheima for a fraction od the price. You can't of course use one with a soil substrate. And there is some merit to Axelrod's original deisgn that used tubes about the outsde whcosould eave rhe middle intace gfor plaants. It's worth playing with. The easiest way is to cut some lighting egg crate grill to fir the tank bottom and cover it with "pet" (urethane) window screening, it wont break down under water in time. Fit in some number of airports growth 1" clear tubes that most fish stores have and you're done. Dolomite for marine, #2 gravel for fresh. Works well.

Encyclopedia Aquatica