I'm using 2 filters right now for our Betta. One is the bio-wheel that comes with the Marineland Hex 5, the other is a sponge filter, which also aerates the tank. There is enough current in the tank to give our Betta a fight. But, it seems he enjoys battling it as there are places in the tank that are current-free, yet he spends his time riding the current flow.
One thing you don't want to do is add the replacement water without treating it first. With water changes, it is always a good idea to make up your water in advance of the
water change to allow the dechlorinater to do it's job and to allow the water to expel any of the gases in it that just aren't good for the fish. I use Stress Coat when I'm not trying to control
ammonia levels in an uncycled tank (then I use Amquel+).
As for the Bio-Spira, wherever you get it, make sure it's been kept refrigerated. If it hasn't, it may be no good. When using it, put the Bio-Spira right in with the fish. The bacteria needs ammonia to thrive and if there is no fish in the water, there's no ammonia source. Typically, you'd want to put the Bio-Spira into the tank first, then put the fish in immediately afterward. The claim is that the Betta is absolutely safe within 24 hours. Though there will be spikes in the ammonia (and likely the nitrites not long after), it's safe for the fish. Do no water changes for 7 days at which point a 25% water change should be done. If you add the Bio-Spira to the tank with the fish already there, try not to dump the Bio-Spira on the Betta's head.
Hope this helped.
Mike