tank problem

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Jul 24, 2004
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I noticed a weird problem with my bettas. I've been keeping them in 2.5 gallon tanks with corner filters divided into two (glass dividers). I also kept one boy in a 5 gallon divided into two, with guppies on the other side. This boy came down with finrot, so I put him in my hospital tank (3/4-1 gallon bowl). He got better, blew lots of happy bubbles, but when I tried putting him in the 2.5 gal setup, tank and filter disinfected, finrot immediately attacked his tail again. It was a rough couple of weeks, but finally he got completely (I believe, as there were no more dark edges, and fin was growing back) cured this week. So I moved him back in a 2.5 gallon all by himself with the corner filter (I disinfected the tank, but the filter was an "established" one). The next day, finrot ate at his tail again.

Anyway, I'm confused. I know bettas are supposed to be happier with larger tanks, but it seems that mine are not thriving in the larger filtered and cycled tanks. The others seem to be possibly coming down with finrot as well. Whenever I move them to the hospital bowl, which is unfiltered but I clean it (full water change) every 2 days or so, they heal well and blow lots of bubbles (even when they're sick). But when I put them in the 2.5 gals, they hardly have any bubbles at all, and they seem to eventually get sick. I clean the 2.5 with 30-50% water changes every 2 or 3 days. Now I'm thinking maybe I should just get all my bettas 1 gallon unfiltered containers each. I wanted to avoid this before as I hate doing frequent full water changes and thought they'd appreciate larger tanks, but I hate even more their getting sick all the time.

Does anyone have any insights or suggestions?

Is it possible that the filter current is too strong, and stresses them? I think that may be the most likely problem.

I would think so, too, but the current is pretty low, I just use an airdriven filter and control the air flow. I've tried putting more bubbles (thinking the filter would increase cleaning), and lowering bubbles (about 1-2 bubbles coming out per second), but they're still not happy. :( I even tried putting current only on one side of the divider with the guppies, as water could still flow from the divider gaps, but still got finrot.
I think you're right. I took out the filter last night and this morning Treasure is doing much better (fins started healing again). I guess he doesn't want any filter at all.

The guppies are fine in their set up.

fourplayfishy said:
its possible if the filter was established that the bacteria causing the finrot was in the filter
i agree, espically since it's only a corner filter and not a power filter. I'm surprised hte guppies aren't affected though...does the divider have holes in it? or is it solid?
The divider is solid. I couldn't figure out how to put holes in the glass without cracking it, but it is held up by a device with suction cups on both sides, the water flows through the gaps. I tried disinfecting a filter (bleached, new floss) with the same results. I'm thinking now maybe they just prefer to have no aeration at all.

Here's a picture of the kind of divider I use (but I keep tanks bare, no plants or gravel):


oh, you should have plants. they like to sleep on them. That minght also be stressing them out. i know mine are very stressed without plants to sleep on.

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