2x fluval fx6 with 4 liters seachem matrix for the bio media total
1x eheim 2260 with 5 liters seachem matrix
total 9 liters seachem matrix for bio media which can treat up to 900gal tank based on the product descriptions (1L treat up to 100gal).
i can do 50% WC weekly, but if i have to do 2 WC weekly i can not. I use seachem prime for the conditioner.
50% I would say is good, for the aro, dats and 1-2 rays. Of course when they grow they will produce more waste, but 140 gpw should be sufficient