Depends on the species of pike, as some pikes have HUGE mouths, where as others have 'smaller' mouths.
General rule of thumb though, is to get a pleco that is AT LEAST half the size of the pike. They have ridgid dorsal and pectoral fins, which they can easily lock down to keep from being eaten. As long as they are half the size of the pike though, they are generally too large to even fit in the mouth of the pike.
I've never had problems with plecos and my pikes, but still use good judgement...
PP-that;s an interesting point about different mouth sizes. How about you give us a catagorical grouping of pikes based on large, medium, and small (relatively of course) mouth sizes? Gotta keep Mr. Pike earning his title !
what kind of pike is it? Some of the more rougher pike will harrass the pleco more than eat it. Like cobra, orange, cincta, Johanna... Never had a pike eat a pleco, just nip the fins.
Buy some? Several people already have them.... They are a relatively common pike depending on the time of the year. The collection time for pikes is pretty much almost over now though, so gettin in smaller pikes will be harder. Which means most of the ones that come in will be either subadult or adults, which will be more expensive as a result of the fact.
Catagorize them by mouth sizes? Oy....well, generally speaking your Saxatilis group pikes are gonna have relatively smaller mouths in comparision to the other pikes. Acutirostris group pikes generally are more compressed, so their mouths aren't quite as large. Lugubris group pikes generally have some of the largest mouths out of all the pikes. However some species from the Reticulatus group have enourmous mouths!! For instance, Crenicichla cf. jegui has a mouth that most other pikes can't even come close to. Its amazingly large. There are exceptions with in the groups, and I haven't really kept enough pikes to know ALL of their mouth sizes, but generally thats the way things go. Oh, the dwarf pikes have some of the smallest mouths...haha.
Taz put a good point. I've never had a pike eat a pleco, but they have harrassed them from time to time. Go at least half the size of the pike, and give it plenty of hiding places. If you pocket book is big enough and you have the availability though, go same size or larger as the pike will definately grow much faster.