They can be fine, but the rate at which you're adding fish is a likely culprit for the algae issues (although the algae really doesn't look that bad).
I would slow way down. Don't add any more fish for at least a couple months while the tank's biofilter has time to catch up.
As for the algae, I'd remove as much as possible by hand and through the siphon when you do water changes. Other than that, it will likely go away over time. It's really not bad at all.