the air bubbles could be from low water in the rear chamber, i usally keep my water level alot higher than the max line, if the water level dosent help it could be that the water if flowing through the rear to fast causing micro bubles. first thing the cartrige in the first section remove it and dont buy a new one, i removed some of the bioballs and put a bag of carbon from a aquaclear 110 filter and a chunk of filterfloss on top under the black thing in the middle chamber, i also used a small slowdown valve from a phosban reactor to slow the water returning into the tank wich helped alot.
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http://www.jlaquatics.com/phpstore/s...t_ID=pf-acr50c
for the algae issue try looking up cyano and see if its what you have, biocubes dont have skimmers on them so you have to be carefull on extra nutrients in the water i do a 5g waterchange every 2 weeks usally but i only have ever had 3-4 fish at at time dont feed extra food and if you can get ro/di water it will help alot