Bettas Succumb In Larger Quarters?

[DWC]

Had eight male bettas in 10 gallon tank segregated in 1/2 gallon jars, tank being a water bath to keep them at 80F. Did 75-80% water changes twice weekly and rotated neighbors! All were happy, healthy and active. Each had a Java Fern in with them. But I felt guilty after joining the board about small living spaces so made 2 identical tanks, each 10 gallons, with one male in each, others rehomed. Now have sponge filter, plenty of Java Ferns, moss, and water parameters identical to before, temp 78-80F, ph7. Have not cycled with single betta in each but tested for ammonia, nitrite and nitrate all still zero. BOTH dead the next morning and hiding first day; before very open and active. Rechecked water, then added two more of the rehomed males to the two tanks. Both hiding and looking poorly. Any ideas? Only "new" variables is slight movement from sponge filters, black aquarium sand, bottles were bare, and Mopani driftwood bought from lfs that was well rinsed. Help please. Should I drain all water and restart?

 

[Ryan10]

Do you have a picture of your setup?

 

[DWC]

No pictures of new tanks, old setup was eight 1/2 gallon jars in 2 lines of 4 nestled in heated 10 gallon tank with Java fern in each jar.

One other variable I did not think of was I added dose of concentrated bacteria starter, house brand from mail order company Dr.Foster in states. Could that be the culprit in now 4 bettas untimely quick deaths in the new tank? Ammonia, nitrite, nitrate, pH and hardness all test perfect match for individual jars in which they lived happily for 6 months. Thanks for any help. David

 

[Ryan10]

Are the bettas able to breathe? Bettas need to breathe air from the surface like a frog.

 

[DWC]

Though there is a glass canopy with LED light above each tank, there is plenty of airspace above water bad below glass and canopy is NOT snug so good gas exchange. I may just cycle now empty tanks and give up on betta for a while trying another small tank species. Just wish I knew what I did so wrong with such dramatic results.

 

[eduller]

A 75-80% water change twice a week is not enough for a 1/2 gallon jar. They could very well have had a lot of ill effects from the toxins in their water, and the stress of moving to a new tank took its toll. It's unlikely the bacterial additive could have caused any harm. I assume you are using water conditioner. Have you added any other conditioners/chemicals/treatments to the tanks?
 
Four of my bettas are alone (with a couple snails) in 10 gallons, and they are thriving.