Question. what do you mean when you say...
Now on to your post.
planning a trip to the keys in may and was planning on bring back some goodies for my first reef tank
Dont wanna burst your bubble but make sure your read up on the local laws if you plan on collecting stuff in the wild. I belive collection in the coral reefs off of FL is illegal unless you have approprate permits or go far enough off shore that your in international waters.
Sure more is better as far as filtration when your talking fish only. But since many corals are filter feeders then having to good of a filtration system will cause your corals to compete with your filters.
I dont use the miracle mud system but basicly its just a refugium from my understanding. I dont have one nor do I run a skimmer.
Taller is better for a skimmer because you want to prolong the contact time the water has with the air bubbles. The longer the contact time the more efficent the skimmer will be.
Flow rates should be at least 10 X the capacity of your tank in my book. Remember head height when factoring how much your pumps are flowing. If youhave a pump on a sump or filter under the tank then its flow rate will be lower than if you had it level with the tank.
Im very confused as to what you describe at the end about your 70. I think you need to redo your setup on it so you hve water going into an overflow at the tank and then down to your trashcan full of bioballs. Then have your return pump going back up to your tank. This way you will never have to worry about the pump taking water out of your tank being faster or slower than the pump putting water back in. Just make sure you size your overflow to accept the GPH
that your return pump will put out.
FYI, would be easier to read if you could seperate teh items into paragraphs.