I think most people are going to tell you that you're already overstocked, though opinions will differ. The recommendation for Otos alone are for them to be in groups of 6 (or at least 2), and in a minimum of a 10 gallon tank. Harlequin Rasboras recommend 8-10 at a minimum, in a 10 gallon tank, and so does the pygmy cory, though I read that it might shoal with other species happily.
I hope this isn't harsh, I know I was super surprised when I read how little was recommended for a 5 gallon tank! Remember that tank requirements are based on both bio-load and behavior needs. For an overloaded tank, you can get a bigger filter (or plant more plants), but there is no fixing a tank that is just plain too small for the fish to swim happily... That said, if your little guys are all settled in at this point, I don't think it's the worst thing in the world to leave them be and be careful with keeping their water parameters healthy. I wouldn't consider the shrimp as part of your bio-load, or to be taking up much space. In fact, your tank is probably better off with them in there! If they continue to reproduce though, you could fill your bowl with shrimp and maybe a mystery or nerite snail, and a bunch of plants.
If you do decide to upgrade to even a 10 gallon, you'd find you could probably add a few more rasboras, and maybe a couple of the others as well -- and their behavior would likely become much more energetic & interesting. I have guppies in 5 & 10 gallon tanks, and in a 29 gallon. I feel terrible for the little guys in the 5 gallon now. They just....sit, motionless, for much of the day. They're much more energetic in the 10 gallon, and the ones in the 29 seem to positively dance, all day long!
For more viewpoints, I would read threads in the "nano tanks" forum, and take note of stocking levels. I think the Spec V thread is probably a good one to read, too! Good luck, and welcome (from another newbie)!
It's not a mystery...snails are the BEST!
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