If you don't go through this process, I'm afraid to say overcrowding will be the least of your worries.. But you've found an amazing helpful resource here at this forum! Good luck and keep asking questions.
What kind if tetra and how many and how many angels? You sound pretty stocked already. Do you have a test kit? Because your tank is only a month old it could be still cycling. That means it could be having spikes in ammonia and nitrite. These are poisonous to fish.
Did you read the article donkey posted? Any questions?