Hi Dean, first of all, do you know a thing about hermit crabs? Have any idea of their basic care, how they are, what they eat, what their requirements are? You just seem to keep wanting to get new animals constantly without researching a thing about them first.
Hermit crabs are very, very delicate creatures and most of the ones you see for sale do not live long because they do not get their requirements. They are far more difficult to care for than goldfish or tropical fish and did you know they stay buried under the sand most of the time? They will not be out and about like your fish so if you are wanting a pet that you will always be able to see or play with hermit crabs are definitely not it.
I'm going to give you a basic run down on what my hermit crabs require (and keep in mind having a pet is more than just giving it the basic requirements it needs to survive!). They cannot live in those painted shells you see, and they cannot eat the hermit crab pellet food at pet stores. They need both freshwater and saltwater pools, deep enough to submerge in.
I have a 60 gallon with about 13 hermits. I have had most of them for years. Yes, they do live for years, not months as the pet stores and mall kiosks tell you.
tank and stand (a tank with wet sand can weight as much as an aquarium)
One pound of calcium-based substrate per gallon, preferably more: (for your 30 gallon) about $30-40
Glass lids for tank to hold in humidity: $20-30
Freshwater pool: $15-20
Saltwater pool: $15-20
Fresh and organic hermit crab food: I spent about $30 on mine this week. They need a different food each night including a fresh fruit or vegetable and something with protein
Sea salt mix: about $10-20
Thermometer and hygrometer (one each for each end of the tank): $20
heat lamp fixture: $10-15
Heat bulb: $7
Hydrometer to measure saltwater content: $20-30
Hermit crab friendly shells, can be about $2 each, need at least 2-3 per crab
Moss and Eco-Earth for bedding: about $20
Dechlorinator for water (CANNOT be StressCoat as it contains a slime coat which will kill hermits): $10
Climbing branches, driftwood, toys, things to hide in: $20-100
Spray bottle, not to spray crabs but to spray tank walls to keep humidity up: $5
Natural sea sponges to keep humidity up: $5
You also need to study up on the different species as there are many different Coenobita species for sale in the states now. Each one has a different temperament and different requirements.
You also need to be committed to adding a new food each night and cleaning out the dish from the day before. They also constantly need fresh water and this can take time (you have to mix the saltwater just right).
So anyway, these are just the basics. As you can see there is a lot involved. I strongly recommend reading up on the following sites as you can find out more about their care. I really hope you listen as I feel the members here have given you great advice in the past and you sometimes ignore it. Do not just go out and get hermit crabs because you see them one day and think they are interesting. I have devoted a lot of my time to researching their care to understand them better and I have a lot of friends that have done this as well.
Hermit crabs are not cheap, easy throwaway pets anymore than goldfish are.
http://www.foreverpurple.com/hca/http://www.hermitcrabaddiction.net/forum/http://www.epicureanhermit.com/mambo/index.php