Yeah flame scallops are challenging, even for experts. That's an animal I do not recommend to anyone.
You may be adding too fast. One fish every 3 weeks (like Ryan said) is good. Fish do not count as a cleaner crew, but they do add to the bioload, so even if it's an algae eating fish, you still need to wait ample time before adding a new one.
Snails and stuff don't count towards your bioload, so you can go ahead and add those as you need them.