Now I've finally given my rainbows away I was left with 1 RTB, 2cory's and a bristlenose plec in my Juwel rio 125. the tank size is 31x15x19 and when I've used an aquarium calculator it's actually 135ltr. I've just added a small group of tiger barbs (six) and seeing how they settle in and if all being well would like to add about 4 more plus a small school of about five cherry barbs. Is this pushing it for the size of the tank and would extra filtration be any help if it was.