I had JUST this experience a few years ago with a 15 litre baby one. (I also hate throwing things away.) It sat in the attic for ages, but this summer I finally set it up with some plants, and after a couple of months moved a tiny group of cherry shrimp in. That will be the limit of the livestock.
Itās a bit of a pain to be honest since (1) you canāt have substrate so plants have to be tied to bogwood or similar, and (2) itās really hard to get in to clean filter etc. without taking all the plants out, and (3) there is little room for floating plants. Iāve now got a new sensibly-shaped tank on the way, BUT having said all this I am really glad I played with the biorb to learn something new before investing in any more kit.
Once the shrimp are in the new tank, Iāll likely try to run the biorb without the filter, i.e. take the guts out, fill it with substrate, and just use it as a low tech tank with a light. Thatās the plan, anyway....