Like Merkinaer suggested - I'd find a very large sponge(biggest you can) on ebay, add your own drilled pvc pipe to a big pump which sits in the centre pushing water towards the surface. You could even run multiple sponges to the one pump, creating a lower flow through in each sponge which is great for beneficial bacteria. The central upward flow creates a great circulation & aeration effect. It will also make sure the side walls of the ICB have a flow downwards which is nice for the fry to encourage a more natural growth pattern as they will sit head facing he oncoming flow. The sponge, if large enough will also provide an excellent biofilm source for the fry.
Run a big shop LED light, ~6500Kelvin, 12hr/day to encourage natural biofilm and algae growth in the system - Helps if the folks forget to feed, but not needed if some decent natural light is available.
Then, if possible, have a second large source of treated water (maybe a second ICB) - With an automatic timer running a pump for "X"mins/Week pumping into the original ICB. Equip an overflow drain out w/ a sponge to guard the fry. This allows for automatic water changes of a certain volume. (figure out the Litre/min rate of the pump, set the digital timer up accordingly.) You can also run a second smaller pump from this same ICB of clean water on a ATO system to account for evaporation.
Something like this is about as low upkeep as possible - could run for months without intervention, just feeding required.