Fatty Jellyfish

If you recall, our daughter requested a jellyfish tank for her birthday last year and we acquiesced and bought her one. The kit came with three jellyfish who survived for five to six months and then perished. They seemed to do alright but just kept getting smaller and weaker until they started losing appendages and just becoming so microscopic that they were hard to even find. 

My daughter spent long hours trying to figure out what was wrong, investigating everything from the salt water chemistry to their food. She never found anything conclusive before the experiment came to an end with the third jellyfish's death. We buried them all under a tree in our back yard in a sad funeral. 

Due to some vacations coming up at the time (spring break), we counselled our daughter to wait awhile until we returned from them before she tried again. She cleaned everything thoroughly, got the water chemistry spot on and even bought food from a different source. The jellyfish arrived and adapted to their new home with very little stress compared to the last batch but never seemed to get any bigger. In fact, they started shrinking again. At a loss, my daughter did more research and wondered if a different type of food would make them grow. Other people fed their jellyfish with brine shrimp that they hatch themselves and just supplement them with powdered jellyfish food once a week or so since it contains some nutrients they need. We decided to give it a try.

The jellyfish have been eating mainly brine shrimp for three weeks before I took these two photos and all of them are growing but the biggest one has gotten darn right fat. He is about ten times the size he started out as and is triple the size of the other two despite him having 25% less stomach capacity. Moon jellyfish typically come with four crescent shaped stomachs and four legs but this one only came with three. You can see his/her/it's stomachs clear full of brine shrimp in the above and below pictures. 

So obviously I think my daughter has figured out that the problem was their diet. The powdered food which is supposed to be all that they need is obviously not enough or at least isn't enough for their fish tank environment. The brine shrimp diet once a day, six days a week however agrees with them very well. This makes my daughter very happy which in turn, cheers me up though with a summer trip approaching, I'm a bit apprehensive yet. She has to hatch and raise the brine shrimp as needed so can't do that from miles away. She does have an automatic feeder that will work with the other powdered food. I have tried to nudge her to ask a friend with a drivers license to come over and check/feed them while we are gone but she doesn't want to do that. So hopefully they will be fattened up enough that they can survive the time away until she gets back and begins to fatten them up again with brine shrimp.



Comments

  1. These sure make for fascinating pets! I'm glad you guys were able to determine what these strange creatures needed Ed... such cool looking things!

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    1. I think so too. My daughter keeps them in her room so I forget about them for a week or two and then suddenly see them and am entranced once again.

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  2. Thank you for this update! Very interesting and your daughter deserves a wreath of gold stars for being so diligent in her research. I think all living things do best on the most natural diet for their particular digestive systems. Much better than solely on formulated, packaged feeds. I use these for our livestock as a supplement, but all our critters are so much healthier and happier with their preferred "real" foods. As good as science is, it is still reductionist by nature, because it's difficult to test the synergy of interactions between living organisms and their environments. We make educated guesses and do our best from there.

    Any idea of their expected lifespan? I hope they live happily to reach it!

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    1. We were told about six months to a year for a life span. Right now the investigation is centering on how best to preserve the brine shrimp eggs. They come in a small bottle but one that is big enough to feed these things for probably six months. Unfortunately after the first month or so, the eggs stopped hatching and we summarized that they are going bad. This time around we put a little bit in the old bottle and froze the rest. This seems to be working out but we aren't getting a month of longevity out of the amount we pour out of the frozen bottle. Our current thesis is that the second bottle was just older to start with (no dates on the packaging at all) so she can't keep as much unthawed as we had thought but that freezing does help preserve them longer.

      I really like this gift that forces her to think, reason and deduct. It is a gift that keeps on giving.

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  3. Oh, I'm glad that she was willing to try again! That in itself would be cause to celebrate. William is only 11, but he has a real tendency to simply accept that there are things that he cannot do. That is a surefire way to not learn anything new.

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    1. My kids do too but fortunately this was not one of those things.

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  4. I've got a question though. Can't the brine eggs simply be put in water, allowed to hatch and then simply go into their own life cycles, making eggs, dying, hatching, making more eggs, ad infinitum?

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    1. Evidently not. Any unused hatched brine shrimp can be put in a refrigerated environment for the next day but after that, they go ahead and die. I don't know the dynamics of their life cycle but I will ask my daughter and perhaps she can enlighten me.

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  5. Well I have never heard of keeping pet jellyfish so this is all new to me. I'm glad the food mystery has been solved!

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    1. It was new to me. I'm just happy to see my daughter research and take ownership of the project, something she doesn't do all the time.

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  6. What a great project! I didn't know you can keep jellyfish in a tank.

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    1. I didn’t either until my daughter did the research.

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  7. Thanks for an update on the jellyfish! I was sad when the first batch died, too. Good for her for persevering until she figured out the right combination for success! I sure hope they survive her upcoming absence. -Kelly

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    1. I hope so too. She does have an automatic feeder but it messes with the water chemistry and as we learned last time, doesn’t adequately feed the jellyfish.

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  8. Jelly fish are amazing and beautiful. I'm very impressed with your daughter's zeal to find out why they weren't thriving and to fix the situation. That jellyfish is a BLOB! LOL

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    1. And that blob is about twice the size it was when I wrote this and has grown a fully formed fourth stomach. It still only has three legs though.

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  9. It’s impressive how she did her research.

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    1. She continues to impress me... at least on this aspect of life.

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  10. Thanks for sharing the follow up Ed. It is comforting to see rational thought and discovery playing out.

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    1. Especially when your children are showing those traits.

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  11. Wow! That's so amazing! I'm assuming these are the kind that are not poisonous. :-)

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    1. They can sting but I don’t know if they are poisonous. However these are so small do to environment, I’m not sure if a human could feel the sting.

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  12. I guess the big one isn't constipated is it? Has she named them? Maybe it's pregnant. What does a pregnant jelly fish look like? She's already done her high school science project! Linda in Kansas

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    1. They do occasionally get a form of constipation especially with the powdered food where it can clump up on their tentacles and not be passes to their stomachs. She has named then though I can’t tell them apart. From what I have read, it takes very specific conditions for them to procreate in a tank and that we probably won’t achieve those conditions. But it that happens, I’ll be sure to blog about it.

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  13. If you pay the cost of my airline tickets, I will be happy to fly over to live in your house and look after the jelly fish according to your daughter's instructions. Please make sure there are plenty of cans of "Schlitz" beer in the fridge.

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    1. I think the current plan of a forced diet is much cheaper.

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  14. Awesome. So glad she figured out the problem and they are thriving.

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  15. These are cool looking jellyfish, something I'm sure is rare in Iowa!

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    1. Yes, jellyfish are extremely rare in our ponds and pools!

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