Anabantid problems.

[wataugachicken]

i don't have a solution, just wanted to say that the same thing happened to me. fine at night, but the next day my male betta and female betta in separate tanks were both completely covered in that white fuzz. i had neons and another kind of tetras and those weren't affected at all.

 

[Beeker]

I have had the Sparkling Gouramis for about 2 1/2 months now. The 3 deaths happened a couple weeks ago. I didn't see any symptoms. It seemed to have happened all of a sudden. They are far less timid than the Bettas were. They sometimes pick on my Ram. They don't seem to be a schooling fish but they do get along well with the other fish and don't seem to be timid.
The Peaceful Bettas which are a certain species of Betta and are the most peaceful and timid fish I have ever seen, I'm pretty sure were dying of this white fungus that was brought on by stress. They all got along great, but they couldn't seem to get over the most simple things. I thought I was making the water changes as stress free as possible but they had trouble dealing with even that! From the day I bought them, they would hide and very rarely come out. When they had gotten used to the tank they came out to eat, but then they would go hide again. I'm considering never getting a Betta Imbellis again and possibly just getting a regular Betta Splendens and maybe a couple of ADFs. But I don't want to make any move at all until I know that I didn't miss something on any special care for that Anabantid type of fish.

 

[Aqualung]

There are some anabantids that are probably equal to discus when it comes to difficulty in caring for them (licorice and chocolate gouramis come to mind), but as far as I know sparkling gouramis and peaceful bettas don't fall into this category.

From what I can tell, it doesn't seem like you did anything obviously wrong. I have to wonder if there was something with your water that didn't jive with them. There's also the possiblity that you just got weak stock. Sometimes things like this happen despite our best efforts.

 

[fantail]

It sounds like columnaris. Bettas especially are prone to this, what temperature is the tank? Imbellis bettas if thats what you had can and do live together peacefully, but ive only seen it done regarding pairs.
If it was columnaris then it starts around the head region and generally takes less than a day to kill and spreads quickly.
Now that ive written this i cant remember if you had the tank size and occupants listed?

found out that indeed imbellis males can be kept together. Its only the breeding of the veils and man made breeds that have the aggression.

 

[Beeker]

It was a 10 gallon tank and I had 3 Bettas in it and a small handful of snails. Two out of the 3 did seem to pair up. They didn't bother the third though. They all got along well, when they came out of hiding. The temp was 79 and it was a planted tank.