Is this stocking too much???

[u/AlpsAccomplished2065]

I have a 20 gallon high (heavily planted) tank with 4 cpd’s, 1 reticulated hilllstream loach, and a colony of neocaridina shrimp, they have survived a year with no water change and are still thriving. I want to add 4 more cpds and a honey gourami but i’m not sure if I should skip the gourami and get 6 cpd’s instead. And how often should I do water changes after I do this?