What size is your tank? 10 gallon
What temperature is your tank? 82 degrees F
Does your tank have a filter? Yes, Aqua-tech 5-15 power filter with bio-fiber biological filtration and EZ-change #1 filter cartridge
Does your tank have an air stone or other type of aeration? At the moment no, but I do own an air stone that I could use.
Is your tank heated? Yes
What tank mates does your betta fish live with? 4 Betta Fish in total, separated by custom made dividers.
What type of food do you feed your betta fish? Zoo Med Micro Floating Betta Pellet Food 0.65 oz.
How often do you feed your betta fish? I try to feed them only once a day and as many pellets as they'd like. They always eat all of them, I never exceed 10. There are other people in my house who feed them so every now and then they get fed more than once.
How often do you perform a water change? Weekly (In my old small 2.5 gallon tank I changed the water 100% weekly, I've yet to change the water in this new 10 gallon tank because I only just set it up last weekend.)
What percentage of the water do you change when you perform a water change? 100% (Again this was when I was using a 2.5 gallon tank.)
What type of additives do you add to the water when you perform a water change? Typically none because I use distilled or spring water but when I set up this new 10 gallon tank I used Tetra Water Conditioner.
Have you tested your water? If so, what are the following parameters? I tested it after I set up the 10 gallon tank and the pH came up high, so I then added the Tetra Water Conditioner.
Symptoms and Treatment
To make thins easier I will provide details on the 4 Bettas I own and a Timeline.
Older Blue Betta, nearly 1 year-old, housed formerly in 2.5 gallon tank, now in 10 gallon tank.
Older Orange Betta, nearly 1 year-old, housed formerly in 2.5 gallon tank, now in 10 gallon tank.
Older Red Betta, deceased early December, housed in 2.5 gallon.
Younger Yellow Betta, purchased 1 month ago, housed formerly in 2.5 gallon tank (replaced Older Red Betta), now in 10 gallon tank.
Youngest Blue & White Betta, purchased 1 week ago, housed in 10 gallon tank.
I purchased Older Blue, Orange, and Red Bettas nearly 1 year ago and they were housed in a 2.5 gallon tank with dividers, a sponge filter, and an airstone. Water changes were 100% weekly, if not bi-weekly at the latest. Water was not conditioned because I used Spring or Tap Water. I left the fish under the care of my grandfather who overfed them while I was on vacation for a week and when I returned the entire tank was brown and all 3 Bettas were gasping for air on the bottom. I immediately went out and purchased a brand new tank (same build) and transferred the fish and began treatment using Betta Revive. While using Betta Revive I turned off the filter and left on the airstone with the Older Red Betta who appeared to be the worst. Unfortunately he did not make it. The Young Yellow Betta was then purchased and replaced the Red Betta after another 100% water change. The Yellow Betta did not take well and was sluggish on the bottom of the tank and the Blue and Orange Bettas began to appear sluggish as well and their fins began ripping with little black coloring along the edges. I read up on Bettas and realized the temperature was most likely too cold and the size of the tank was cruel so I went out and purchased a 10 gallon tank. I set it up with dividers, plastic plants, the new filter, a heater, a thermometer, distilled water, and Tetra Water Conditioner. I let the tank sit for 24 hours then acclimated the 3 Bettas as well as a brand new Betta I purchased the day prior. I then released the Betta's in the tank after an hour and everything seemed fine until yesterday. I noticed the water cloudy despite a bigger filter and size tank and the Blue Betta, Orange Betta, and Yellow Betta's fins have taken a turn for the worst. Black frayed edges everywhere and now their pectoral fins are destroyed with little white spots. The Yellow Betta even has black visible on his gills. The Orange Betta has a goldish look to him (which I read could be Velvet, or perhaps I'm paranoid now) and developed a white spot on his mouth where the color has come off completely. I administered Betta Revive to all fish this morning but left the filter on because when I tried to turn it off the fish instantly appeared sluggish and got me worried. But I went to check on them now in the afternoon and their condition seems to be worsening. The yellow fish's dorsal fin is no longer flowy but seems to be stuck together. I'm very concerned. The youngest Blue & White Betta seems to be ok for now but I'm afraid everything will spread.
I'm considering doing a 50% water change, changing the filter, leaving the youngest Betta in the 10 gallon tank, and moving the 3 sick fish to the old 2.5 gallon tank and medicating them all with 100% water changes and salt I've heard works? But I think moving them from tank to tank will stress them out and make them worse. I will attach photos in a following post.
Thank you for all your help.