I know very little about puffers. I rarely have had any. The problem is some people say they are like Boxfish/cowfish in that they can release toxins when stressed or they die. My customers do no want to take that chance, so they do not choose them for their tanks. If they can release toxins like Cowfish; we know that fresh activated carbon can remove it. I therefore would have two filters with carbon. I would clean one and replace the carbon every two weeks. If done in rotation that would be cheap insurance.
I personally do not believe there is any shark that can be housed properly in a tank below about 1,000 gallons. They all grow too big for a 150 very quickly.
Eels are great but need a special set up as they are escape artist. They can and do get out very small openings in tanks. They love to explore at night. Plus you would need a LR pile for the eel to live in and feel safe. The same with puffers, they need cover.
As to clean up crew, yes the puffers may eat them. But I would still add the detrivores before the fish and let them multiply for 3-4 weeks before any fish go in. They can help a lot and provide live food. I would definitely use Live Sand, as puffers like to blow sand looking for food. They also need to be feed less than most people feed them. But they need algae in their diet along with hard foods like snails crabs and mussels in their shells. Puffers have teeth that never stop growing and need the shell animals to help wear down these teeth.
As to tank mates, I hope someone with more experience with puffers will correct me If I'm wrong. I would think a Rabbitfish( remember they have venomous spines), Tangs, Butterflyfish, and some of the wrasse like the luna wrasse - Thalassoma lunare. might be good tank mates.
The books all reccomend protein skimmers for these fish, however I've seen them kept without one. If you change your filter media regularly and do your water changes; I see no reason you can't keep one healthy without a skimmer.
Best Wishes,
ray
