It depends on how much time you have to devote to the pet...
With turtles you need both land and water and as with any cage it needs to be as clean as possible. exoticpets.about.com
not sure which crab you are looking into but hermit crabs a fairly easy keepers... exoticpets.about.com
humm porcupines, well they aren't commonly kept as pets and finding one may be a bit tricky. Keep in mind it is illegal in some areas to keep wild animals as pets. Hedgehogs are slightly smaller and can be quite a nice pet I considered getting one myself.. www.mihog.org
I have raised tree frogs from tadpoles, quite fun... I had a 10 gallon terrarium with one side water and one side land... A few plants, water filter, and tree like wood or vines easily found in pet stores. Not hard to hard to care for but in some areas it is hard to find the really tiny crickets and fruit flies for the super tiny baby frogs. www.livefood.co.uk
Gerbils are quite hyper, had one myself. Male rodents tend to smell more so keep that in mind. Most say to keep them in an aquarium but the ammonia smell tends to accumulate a lot more so I would recommend a sturdy wire cage. The bigger the cage the better. They are big chewers and tend to destroy cages so plenty of chew toys are a must and are easily found at pet stores. Paper bedding is better for their health many breeders say pine shavings are bad for them. Cages have to be cleaned quite often so if you don't have much time this may not be the pet for you. Hamsters and mice are a little calmer but if you are set on a gerbil then a gerbil it is.
www.aspca.org
With turtles you need both land and water and as with any cage it needs to be as clean as possible. exoticpets.about.com
not sure which crab you are looking into but hermit crabs a fairly easy keepers... exoticpets.about.com
humm porcupines, well they aren't commonly kept as pets and finding one may be a bit tricky. Keep in mind it is illegal in some areas to keep wild animals as pets. Hedgehogs are slightly smaller and can be quite a nice pet I considered getting one myself.. www.mihog.org
I have raised tree frogs from tadpoles, quite fun... I had a 10 gallon terrarium with one side water and one side land... A few plants, water filter, and tree like wood or vines easily found in pet stores. Not hard to hard to care for but in some areas it is hard to find the really tiny crickets and fruit flies for the super tiny baby frogs. www.livefood.co.uk
Gerbils are quite hyper, had one myself. Male rodents tend to smell more so keep that in mind. Most say to keep them in an aquarium but the ammonia smell tends to accumulate a lot more so I would recommend a sturdy wire cage. The bigger the cage the better. They are big chewers and tend to destroy cages so plenty of chew toys are a must and are easily found at pet stores. Paper bedding is better for their health many breeders say pine shavings are bad for them. Cages have to be cleaned quite often so if you don't have much time this may not be the pet for you. Hamsters and mice are a little calmer but if you are set on a gerbil then a gerbil it is.
www.aspca.org