| Airation is not going to be too big of an issue for a betta fish, they are naturally found in small bodies of water, almost puddles, and so they have evolved to be able to use air from the surface to suppliment the lack of O2 in the water.
To be honest, you are already way ahead of the general population in that you are worrying about your fish so much. I am still amazed at how many just goofy things are sold that people put betta fish into! Anyways, you could either put a fake plant right underneath the filter return flow to sort of diffuse the current or create some other type of 'sheild' for the betta fish to sit underneath.
In my 10 gallon fry tank, I had to use a filter that was meant for a 55 gallon tank because I set the fry tank up in one day. To help out with the current, becaue the little fry couldnt swim anywhere near the surface, I put fake plants that were long enough to be buried in the substrate, but still float on the surface right underneath the filter. This breaks up the water quite a bit and the fry usually hang out underneath the plants most often. I also put a little decoration of a miyan temple for the fish to find shelter in and this worked out for a long time. I now have the right filter on there since I cloned it by hanging on the 55 gallon tank that I took the other filter from. |