White fuzz on gill

[GVeers]

Housing
10 gallon
Gravel bottom, live plants and ornaments.
Heated, 80 degrees
Filtered
No aeration
No tankmates

Food
Rotation of Bio-Gold pellets, some generic betta pellets, freeze-dried bloodworms, freeze-dried shrimp, and frozen peas
Once a day, 3-4 pellets

Maintenance
Bi-weekly water change of around 50%.
Only additive is water conditioner.

Water Parameters
Tested several months ago
Ammonia: 0
Nitrites: 0
Nitrate: 0
pH: 7.6
Hardness: unknown
Alkalinity: unknown

Symptoms and Treatment
Betta has a white, fuzzy growth on his gill that seems to be getting bigger. It looks similar to a growth he had a few months ago, except it's now noticeably fuzzy and larger. The first time might have been a zit (?), but now I'm suspecting columnaris. He is also staying on the bottom of the tank and avoiding use of that fin. So far I've done a water change and lowered the temperature a few degrees.

At what point can I medicate for something like this? I don't want to jump the gun, but I also want to nip this in the bud if possible.... Thanks for looking.

[GVeers]

Update:

We noticed Betta's condition on Monday. We did a 50% water change on Tuesday, and another 25% on Wednesday. His pectoral fin is seriously hindered and it basically looks like there's a cotton ball in his gill. I would like to consider antibiotics although I'm not exactly sure what to treat him for. Here are a couple somewhat better pictures...you can see the fuzziness right below his pectoral in each picture:

[Pataflafla]

Put him in a smaller container and float him in his main tank. Mix up some water with aquarium salt at 1 tsp/gal and use that for the water in his container. Let him get used to this dose for 4 hours before doing any changes.

After that time period you can safely bump up the salt to 2 tsp/gal, but it has to be aquarium salt or plain Kosher salt. Never use table salt.

While using this treatment, you'll want to change as much of the water as you can daily. If there's no response from the fuzz within 2 days, move to either 3 tsp/gal or stop all salt and switch to a fungus medication.