Dwarf Puffer Performing Somersaults

Has anyone ever seen this before? 

One of the dwarf puffers I got a few weeks ago is slowly swimming around, generally investigating the plants and doing puffer stuff. Then it points itself nose down, continues turning on its vertical axis until its tail has gone all the way over, so it's basically upside down, then twists on its horizontal axis, so it's the right way up again, and continues on its was to the next thing to look at.

Is this a sign that the puffer is ill? 
Is it a sign that my puffer is going mad? 
Is it a sign that I'm going mad? 

Seriously, I've just watched it do three somersaults with a half twist in less than a minute.
Or is he just practising for the Rio Olympics?
 

I have just sat by the tank with my phone for 15 minutes and the sneaky little puffer is just pottering around like nothing happened. 

Some of my fish do something similar - swimming with the nose in the substrate looking for food then spotting something interesting, investigating so that the head stops but the body carries on till the fish has turned on its back, then flipping over sideways to get the right way up. The honey gouramis used to to this regularly.

So the question is, was the puffer just swimming about or stopping to investigate something?

Thanks all for the advice and scores.
The puffers have bloodworm at least once a day, but I will see if I can get them interested in the other suggestions as well. Recently they have also had baby snails (apologies to those who have posted snail pictures), and live daphnia.
The first and second somersaults were while the puffer was looking at different plants, but the third was in open water.
He is still just pottering around the tank, I'll keep an eye on him, and attempt to film any more strange behaviour if it happens.
 

Well, just before the somersaults said puffer had been surfing through the filter outflow wave, so perhaps he'd just given himself a surprise enema and was tying to use centrifugal force to clear out the excess water from the uncomfortable areas. 
Well, it's possible. 

The problem with having 11 dwarf puffers in one tank is that it can sometimes be difficult to tell them apart. In a tank with lots of hides, it's also quite difficult to find them all. Breakfast time soon, so I'll check them all then.
The acrobatic one was either the littlest one from the first batch, or one of the second batch, because it wasn't big enough to have matured, so couldn't tell you the sex.
As the puffer seemed fine for the rest of the evening I'm hoping it was just investigative acrobatics, like Sue's honey gouramis.
Fiona, there has been a lot of tail bending from fish in the tank, and some chasing & nudging of females by the mature males, so I'm guessing that they are all limbering up for Spring. 

Well, I've never heard it called that before, but another one to make me laugh this morning.