Yeah my tank is 24 inches tall by 20 wide by 18 deep. I was thinking about a few hatchets myself, but the killifish are doing well as a top layer fish. Definitely looking into the calico or albino bristlenose as soon as my tank starts growing some algae.
You don't need to wait for algae, just buy em some fresh veggies and Algae Wafers. Also, Plecos aren't really algae cleaning machines, they poop a lot as well, so don't just get em for Algae control. Get em cause their awesome.
My blue gourami went after my dwarf gourami when I first introduced him to my 75 gallon tank, so I removed the blue gourami and placed him in a plastic container for 5 minutes before returning him to the tank. Now both gouramis get along just fine.
I was thinking of doing this as well. Well, with a bucket and a power filter for a few hours.
When I added Harlequin Rasboras to my Betta tank and he flared and chased at them I tapped the glass to scare him every time he would flare, or chase and he quickly learned not to chase them. He's been with them for over a month now and no problems there.