pumps out pillows of subwassertang for the lfs, I get a harvest every 2 mos. was able to get some last year from our sellers forum and its become my fastest grower!
last couple years occasional ei ferts as mixed by poster aquarist best fert mix ever
good cherry shrimp ( bred back to wild) 100 ish all interbred, more for farming and self sustenance in the tank
principle poop pellet deliverers.
I siphon some adult shrimp out at times to make room for new, these aren't color breeders they are for performance.
wild type guppies work too, but shrimp fare better with long slow nutrient input imo.
and the key to an unending sandbed doesn't need replacement so far 13 yrs is:
flourite and possibly two pounds of laterite powder at the very bottom. if I could go back in time id change nothing on this tank. its a slow galapagos tortoise. ages sloooooowly
the goal was hands off self sustenance as long as possible between feeds, wchanges etc.
im awr of the various choices of substr options and how much cooler looking and initially nutrient balanced the pro substrs are
amano etc. That's what I use in my micro tank for the undeniable best look.
but I didnt want something with a bell curve life span when doing this tank, it was the lowest maintenance ecosystem I could design. something with normal maintenence infrequent water changes but it lasts forever. No electricity other than the light, and even then I did window light only for mos when my ballast went out. its tough, no heating no pumps.
a substrate that must release nutrients from the bottom is finite, but hard packed large grains like flourite chips simply have an amazing break down rate, in the order of decades not years. im close to 13 and the grains are the same. This creates an exchange option with the upper water table after 36 mos + much better than ball substrates do as they break down around then it seems.
The non breakdown is key imo.
open channel exchange and access.
the open spaces between grains take on mass indefinitely and you can siphon top layers without bed destruction, h sulfide emissions etc
export the sandbed lightly top two inches via standard bed siphon occasionally, to prevent total bed incursion yet the pelleting never stops so its clean, recharged pellets storing up, not just rotten waste from 8 yrs ago under a thin mix of new leaf litter and shrimp waste, the ability to occasionally clean siphon around the plant roots makes the nutrient tables refresh over and over
this sand started low nutrient compared to pro stuff didn't grow as well. its a rate that starts slow and finishes very strong, and very long term while the pro beds start ideal and then become rejecting to top down particle incursion and they eventually collapse which doesn't recycle nutrients well at all. Reading about bed replacement in the amano setups in 2002 is what made me not want to use them.
imo in hindsight, the laterite is expendable and might eventually yield less iron but I claim just cheating a little bit with ei ferts w make up when its multiple decades old.
if someone out there has pics of a sandbed that's old, post pics