So finally switched filters on my tanks. Threw my Eheim ECCO pro 2232 on the 12 gallon long with a spraybar I salvaged from the SunSun 304B that I tacked onto my 40 gallon Amazon tank. Both tanks are doing well and I did a water change after filter transfer on both tanks.
Filled the Amazon tank filter with lava rock since it has a good surface area and for 4 dollars, I got maybe 10-15 pounds at HD. There may be other more porous options like pot scrubbers but I don't know where to find them for cheap haha
Lava rock will definitely be fine.
I did water tests on my shrimp tank today and my nitrates apparently are between 80 and 160 ppm. I will be doing a water change very soon (aka when I finish my dinner). Ammonia and nitrite are solidly at 0 ppm. Any thoughts to why nitrate is so high? It's strange. I don't think there is that much decomposition. I dumped out the dirty water from the canister when I transferred it but did not wash the biological media so that I wouldn't kill any bacteria.