A slum tank locally in Singapore means a tank below the main tank which water is prefiltered and passed through media before being pumped back up into the tank.
it's a standard slum tank design. I don't use any special media, just sponge to catch the downflow, wool to catch the finer sediments, koi mat for support and ceramic rings. This is powered by a eheim 1264(4500 lph).
Same goes for the bucket filter 3000lph and normal 2000lph powerhead.
This system takes 30mins to clear the water to crystal, even with ray after birth, so I have to scan the sand regularly to watch for hiding pups. The LeoPearl gets aggressive when she is pregnant.