jrd77 said:
Your water changes look fine to me.
The carbon: Ok, this has long been a pet peeve of mine. The manufacturers of these filters make these little bags that we have to throw away in order to change- so they make more $$ of course! What I do is this:
I cut very carefully along the top of the bag and shake all the old carbon out. I then take a high quality carbon, Marineland has a good one, and rinse it in old tank water so as not to get *any* chlorine in my tanks. (ok, so I'm a little anal but it works for me!) I then just fill that old bag with the new carbon. It won't GO anywhere once it's in place in the filter, don't worry about the top being open.
Alternatively, you could just fill your filter media bags behind them with the new carbon of course- this is just for future reference I tell you my methods.
But yes, by all means, get some new carbon in that filter without destroying your existing bacteria.
There are lots of air pumps on the market, but personally I use Aquarium Pharmaceuticals RENA Air Pump 400. They also make smaller models. The pump is then hooked up with airline tubing (very cheap) to an airstone or airwand. Personally again, I use an airwand because I like the smaller bubbles. Be SURE to buy a CHECK VALVE and install it between your pump and tank. This prevents your tank water from syphoning out should your air pump fail. Do NOT forego this item- it's very important. Bury your airstone/wand under the gravel along the back (or wherever your heart desires really) but not too deeply under the gravel so as to impede the bubbles too much. In fact, for now, don't bury it all all. Just attach it to the back wall with the suction cups provided. Once the tank is clear, then bury it.
Your fish will greatly benefit from an added airstone/wand. I don't run any tanks without one. They disperse the water so the filter is more efficient and as I said before, help to break up the surface so as to allow more oxygen into the water.
Hope this helps!