Ok so I ran your aquarium size and current stock through the AqAdvisor website. I will put the link down below (its super long). Please keep in mind that the info this website generates is not necessarily 100% accurate by any means, but we can use it as a starting point.
Not sure what you're running as a filter, but I put in an AquaClear 30 hang-on-back to give a baseline. You can modify your filter on the website and add a second one if you happen to have two.
According to AqAdvisor, your current stocking level is 77%, which means you might technically have a bit more room. But, the site did pop up a couple of warnings with the info you gave:
Warning: Serpae Tetra will likely to fin nip Angelfish.
Warning: At least 5 x Kuhli Loach are recommended in a group.
Warning: You should add more aquarium filtration capacity. (again, assuming you just have a standard HOB filter)
Personally, the only thing I would add would be a few more Kuhli loaches and I would beef up the filtration. However, you may be able to add a few more fish if you increase your water change schedule. Good luck!
Definitely check out the website at this link:
https://aqadvisor.com/AqAdvisor.php...qSpeciesWindowSize=short&AqSearchMode=simple&
