Warning: I have a bad habit of spelling Aglae as either Algae or Algea. I do mean the same thing both times I'm just horrible about catching the mistake. T_T
Aglae will happen in a healthy tank set up so it is not a sign of dirt or neglect. The algae appears in newly established tank systems because algae feeds off of the same stuff as beneficial bacteria and plants. Since you don't have any plants to out compete the algae, the algae can grow in place of live plants. That's why you are seeing every color of algae under the sun when you change the filter cartdrige. Not only do you not have live plants to out compete the algae for food but you also remove the beneficial bacteria that was out competing the algae for food. You are unintentionally making an algae paradise. XD
I'm going to give a few quick pointers to help control algae and than explain my reasoning. If I am making an incorrect assumption about your set up, let me know. :)
Do you have lights on during the day? If so, what is the watt and wavelength? If you leave an aquarium light that is 8-13watts and a wavelength of 5500-6500 Kelvin on for more than 10 hours a day, you can get algae whether you have live plants or not.
I get algae in my filter as well because of how close the filter is to my light. I don't know if you have a traditional hood light like I do, but if you have a light that pivots, you can move it a bit so it doesn't shine directly onto the filter. I just ignore the algae as long as it's hair algae (the green, stringy kind) and doesn't grow directly onto my filter cartdrige. If it's on the outside of the filter casing, I just knock it off once a week when I do my partial water change.
To be frank, it sounds like you are at the phase in a newly cycled tank to have algae growth. It's like tank pueberty, all you can do is ride it out until tank adulthood. Leave your filter alone, adjust how your tank gets light, spot clean the areas with the most algae, and let your tank age. That is all you can to do. :)
Last edited by SnowySurface; 09-18-2012 at 12:41 PM.
Reason: added a note