OOPS!
Well, Anglers dont move around much do they? My lion hides under a peice of rock, and he dosnt really bother him - the only time i've had problems is at feeding time. The hermit used to go for the lion at feeding time - but i got around this by directly feeding the hermit first.
As regards to feeding the angler freshwater guppies - can you get saltwater guppies? or mollies? This would be much better nutritionally, though im sure the FW guppies are until you ween him over, right?
Im not too well up on what the eat, things i would definatly try (instead of guppies) would be Ghost Shrimp - ive heard of a lot of people using them to ween anglers/leaf fish over.
Someone else will be able to give you more info im sure.
James