The main reason I keep this website is to offer potential hermit crab breeders a place to observe my process in a very honest way–what has worked and what has failed. Here are some solutions I’ve found for some of the most common questions/concerns that arise.
Q: My zoeae are starting to look sluggish.
A: Your first and simplest response should always be to initiate a 50% water change. The biggest issue is nearly always poor water quality from overfeeding, poor waste removal, or a shed day (with tons of shed exos swirling through the water). In all of these cases, the water change will help. My mantra in this situation is: “The solution to pollution is dilution.”
Q: The saltwater inside the kreisel has gotten really cloudy all of the sudden.
A: This is most likely because they have entered what I call a “shed day.” Every 3 days or so, healthy zoeae will molt and morph into the next larval stage. This is a good thing! It means they are growing and are one step closer to being land hermit crabs. However, shed days foul the water very quickly–especially if you are keeping thousands of zoeae in the kreisel. The sheds are nearly invisible and they break up quickly after the zoeae simply swim right out of them. If you want to determine with certainty, turn off the bubbler and shine a bright light directly overhead. The sheds will look like ghost zoeae–clear, no eyes, and drifting in the water column. Your best bet is to do a 50-75% water change–and don’t forget to turn the bubbler back on!
Q: My zoeae are mostly in a clump at the bottom.
A: First, do a water change. (Are you seeing a trend here?) If that doesn’t help, check your salinity. Too-low salinity makes the zoeae less buoyant and too-high salinity makes them stressed and less motile. Either way, if the salinity is off, they will sink and clump.
Q: Some of the zoeae that are dying appear to have a very straight tail or a dark area near the base of the tail.
A: These zoeae have likely consumed the egg casings of unhatched brine shrimp, which can clog their digestive tract and kill them when they are unable to eliminate waste. Try your best to serve only the orange, freshly hatched brine shrimp, without the dark brown casings.
Q: I’m seeing dead zoeae that are a bright pink color.
A: This occurs when water temperatures are too high. Like living shrimp, zoeae should be clear to opaque in appearance. If they are dying and turning bright pink, they have essentially been cooked by the overheated water. If the water temps are fine, but you are still seeing these bright pink bodies, check the placement of your heater. It may be situated too close to the inner drum of the kreisel (like the bottom, if it’s underneath).
Q: My zoeae are floating upwards (rather than swimming freely) with small bubbles attached to their tails.
A: This is a water quality issue. I’m not certain what causes it (ammonia? nitrates?) but a 50% water change will solve the problem and the zoeae will be fine.
Q: My brine shrimp (artemia) aren’t hatching and I have nothing to feed the zoeae. What should I do?
A: It can take up to 36 hours for brine shrimp to hatch. If you have waited and still aren’t seeing any, here are a few ‘hacks’ that might help:
1. Don’t use a dechlorinator in your hatching water. The chlorine in tap water actually helps to break down their hard outer egg casing. The small amount still present when you feed them won’t harm the zoeae.
2. Make sure the temperature of your hatching water is at least 81 degrees Fahrenheit–continuously.
3. Add a bright overhead light to your hatching setup for 15 hours a day.
4. If your tap water is especially hard, adding a tiny pinch of baking soda to the water will help increase your hatch rate.
5. Open a new packet or bottle of whatever brand of brine shrimp you use. (I like the San Francisco Bay brand.) If not kept in the freezer, brine shrimp eggs can have a much lower hatch rate and they DO expire. Simply trying a new package may be the answer to your problem.
Q: I add nannochloropsis and brine shrimp at night, but by morning the kreisel water is completely clear.
A: This means they are eating everything overnight and you can probably feed a little extra nanno and freshly hatched brine shrimp before you turn out the light. The nanno will also be eaten by the brine shrimp and make them more nutritious when eaten by the zoeae. Feeding brine shrimp that are alive does not create as heavy a bioload as feeling powdered food or dead brine shrimp, so you can feed a little more. It’s a great time for the zoeae to feed (overnight) and it’s an easy method for you.
Q: My kreisel has grown a brown, slimy film on the inside.
A: Siphon everything out into a large bucket (with an airstone in it for the zoeae) and wipe down the empty interior with paper towels. Replace the airstone, add fresh saltwater and the zoeae and continue as usual. You can do this once a week if needed.
Q: It’s been more than 18 days and my stage five zoeae are not making megalopa.
A: Have you been adding nannochloropsis to their saltwater? There appear to be lipids present in nannochloropsis that help the zoeae make that difficult shed from stage five to megalopa. Also, be sure to check for any new megalopa first thing in the morning as they often transition overnight or in the early hours. At 6am, I turn on the light, feed them, and stand by to wait for megalopa. As soon as I see them, I remove them from the kreisel and place them in the transition tank as the stage five can be ruthless killers of newly transitioned megalopa.
Q: My megalopa have been in the transition tank for more than a week but none have come out of the water in shells.
A: There are several things to check.
1. Are your shells tiny enough? The shells they choose are most often small enough to fit under a fingernail, basically the size of a large grain of sand. If the shells offered are too large, they can’t carry them or even keep them situated on their thin megalopa tails.
2. Is your exit ramp too steep? Megalopa need to be able to safely make the climb without fear of falling backward and losing the shell.
3. Do you have a very bright light shining right over your exit ramp? A bright light from above can help encourage them to walk toward the “sun.”
4. Have you placed some small but tasty food items on the ramp to encourage them forward and give them energy for the trip? Bloodworm or gammarus shrimp are reliable favorites.
5. Do you have multiple possible exit points? Some megalopa seem to prefer to climb a twig, a rock, or a clay ramp to exit the water. Give them lots of options.
6. Have you placed a few shells very close to or even beyond the water line? Some will exit and find a shell after they have left the water. I usually place these opening side up, to encourage them to shop.