My betta is in a 1/2 gallon fih bowl and he has a decoration that almost comes to the top of the water (the water isn't at the rim but is 20% away from the rim) And the betta seems to like to swim over the top of it and sit their for a few seconds. And I noticed the his top fin comes out of the water a bit. Is this ok or should I ad more water so his fin doesn't dry up or get damaged by being out of the water.