
Found these on the wall of my freshwater tank, does anyone know what they could be?

Found these on the wall of my freshwater tank, does anyone know what they could be?
I want to buy some copepods to add to my freshwater tank but all the ones I'm finding online are intended for reef setups. Does anyone know if they will survive in fresh water or is there a separate species of copepod I'll need to buy?
(Photo is of a tiny freshwater copepod I saw once)
What's considered low-stocked?
I have a 15 gallon tank (60l) currently cycling. If I wanted a filterless, no co2 tank, how many fish could I safely have in there while still keeping it low stocked and low maintenance?
Would five Honey Blue Eyes, and five Red Neon Blue Eyes be too much for the tank to handle without a filter and without regularly gravel-vacuuming?
Currently there are about 15 ninja shrimp in it.
I'd be willing to compromise and keep the HOB filter on. My main focus is having the tank balanced enough that the cleanup crew and microbes can deal with the fish waste rather than me having to siphon it up.
More info:
It will be decently planted with Ambulia, Stauragyne Repens, and Milfoil
Dimensions are 60x30x36
Light is Chihiros B60
I'm new to this so please, if I'm doing something stupid, tell me :)