Mold Treatment for Tank

[Dressage]

Sorry if this has already been answered, but is there a safe product to use to treat a tank that has white fuzzy mold growing around the edges of the tank at the top of the water level? This is a 20 gallon tank with only 1 betta fish in it. I clean out the mold every week when I do a water change, but it would be nice to find a product that would combat it. Its not a terribly large amount, but I am sure it would be if I didn't clean it once a week. Just as important, is there a way I can maybe prevent this from happening in the first place? Here are the aquarium stats:

Housing
What size is your tank? 20 gal
What temperature is your tank? 79
Does your tank have a filter? Yes (Aquaclear Biomax)
Does your tank have an air stone or other type of aeration? No, but the filter makes a lot of air bubbles under the surface
Is your tank heated? Yes
What tank mates does your betta fish live with? Zero

Food
What type of food do you feed your betta fish? Aqueon Betta Food (Granular/Pellet)
How often do you feed your betta fish? 2x per Day

Maintenance
How often do you perform a water change? Weekly
What percentage of the water do you change when you perform a water change? 50%
What type of additives do you add to the water when you perform a water change? Hmmm...the Stresscoat one and sometimes Seachem Prime
Water Parameters:
Have you tested your water? If so, what are the following parameters?

Ammonia: 0 ppm - low range
Nitrite: 0 ppm
Nitrate: 0 ppm
pH: 6.8
Hardness: 25 ppm
Alkalinity: 40 ppm


Thanks in advance.

[tpocicat]

Does your betta eat all his food? Mold can be caused by extra food. All I can think of.

[youlovegnats]

100% water change and scrub down everything with hot hot water. Mold is something you do not want in your tank.
You can also use a small amount of bleach diluted with lots of water and keep rinsing until you think it's all out, then let it sit in the sun for a day or two.

[Dressage]

Thanks for the replies.

-Yes he eats all his food (I watch and take out any that he doesn't eat).

I will try the cleaning everything again. I guess I am sort of perplexed because these were new tanks and I thoroughly cleaned everything in hot water/super diluted bleach before I put any fish in.

I got to thinking about the filter I use-Aquaclear Biomax. It has a "biological" filter component to keep "healthy bacteria" and such in the system. I'm wondering if this may be allowing the mold that is in my tap water (I presume thats where its from anyway) get a foothold. Has anyone used an Aquaclear Biomax filter before?