Depending on size and how many you are thinking. They grow fast so just prepare to move some or sell some. Honestly a 65g would barely house an adult fh. And depends on what type of fhs you are getting. I would say 5 to 8 max if you starting them at 1 inch to 2 inch.
Sorry I was thinking flowerhorns but you meant blood parrots. Man too much to drink tonight lol. But like I mentioned before depends on the size you are getting. I would do a max of about 10 to start out.