The Post – The Fiddler Babies: Death, Another Pregnancy, and the “Status Quo” Experiment.

Okay. I’ve been silent on the fiddler crabs for the last week. It’s been a week. First, let’s cut to the chase. I lost again on the babies. But again, I have more knowledge on what worked and what didn’t, so next time, I might be closer to an answer. But before I get into that, let’s back up to where things were at last Wed afternoon:

Notes from Wed afternoon:

The ammonia monitor is still partway between “alert” and “safe.” The dipstick nitrite test is down from 0.5 ppm but “not quite” zero. There’s a “trace.” I redid the nitrite test using a tube test, which verifies that. The tube test result showed <0.25 ppm nitrites, but not zero. Still, an improvement.

Numbers of fiddler babies is down some more, but still many. I got some frozen baby brine shrimp and the fiddler babies seem pleased with that.

By the way, PetsMart had three or four kinds of frozen brine shrimp, all of which were little brown frozen cubes. Except for one, labeled baby brine shrimp and it was pink and clear. The lady there said it was the best of the three and was the only thing she gave her fish. It’s called Hikari Bio-Pure Baby Brine Shrimp. It has 40 little pink frozen cubes. I used about half a cube to feed the babies. They are smaller cubes than the ones in the other packages but then, they are really the Grade A Prime frozen baby brine shrimp. 🙂 So they survived not getting the live stuff.

RE the water quality, I also decided to add some of the API Stress Zyme liquid I have. It’s supposed to be a biological filter booster. The man at FishPros said those liquids don’t do that much as they don’t have the right bacteria, those only develop over time, but still said it doesn’t hurt things. So I added some. Figured any boost to the filtering wasn’t a bad thing.

And call me weird, but since the “clear water” in the tank represented a decline in water quality, and the turbid white cloud water was an improvement (turbid because thousands of tiny fiddler babies were churning up the aragonite sand), I decided to act like a “large fiddler baby.” I took my plastic spoon and stirred up the sand on the bottom myself. Curious to see if that helps things. It also stirred up food sitting on the tank bottom that hadn’t been eaten. Perhaps that’s a good thing too. I noticed many tiny fiddler babies flying around in the swirling food, so I think it’s the fiddler baby equivalent of a buffet….


Clear water. No babies. Ammonia level slipping back up to alert.

Friday, Saturday, Sunday

No babies.


Water quality – ammonia indicator almost back down to “Safe.”

So. What happened?

This time around, the nitrites never got anywhere near as high as the last time. The babies were doing great and loved the aragonite sand and the reef rock. All was on track. Then death was sudden. Now certainly I know you can lose a lot of them during their first few molts. No doubt that might have been some of it…though between the aragonite sand and the reef rock, they had adequate calcium for molting. The live rock was growing a healthy crop of algae cover. And they had brine shrimp to follow up the Small Fry liquid fish food and the Kent Marine ZooPlex, all good foods. So they were getting the right foods, and enough food. And they even got more air than the last group because I took the big air bubbler that was in the brine shrimp container and moved it and its air pump over to the babies’ tank. In fact, that may have helped keep the water quality between the safe and alert range for ammonia.

I think my engineer husband put into words my own suspicions, the one nagging concern I had all along, and it’s the one unanswered question in my mind. Salinity. Either the change in salinity from brackish to marine was too much for them, or that change affected something else in the tank that did kill them. The fact that they all died off in one fell swoop very abruptly, indicates again, something tank-wide that affected everybody.

Re changing salinity from brackish to marine – maybe out in the estuary, the transition from brackish to marine is slower and hence they adjust fine with being at sea. So perhaps even though I raised the salinity in stages, maybe it was still to abrupt for the tiny larvae.

Or maybe they really just don’t tolerate a marine environment no matter what the research papers say. These are the species of fiddlers that like things to be the ‘least’ marine.

Another problem though in switching the tank from brackish to marine, is that you are possibly disrupting the “stability” of the tank’s nitrogen cycle. For one thing, I read that as the salinity goes up, so does the pH. Once the pH rises, the nitrites and ammonia levels rise. As nitrites rise, the nitrogen cycle has to absorb that. Not a problem if you have a mature tank that’s been established for that pH and salinity. But if the balance is messed up by changing a parameter like salinity, maybe that disrupts things enough, at least for such tiny creatures as larvae.

I don’t know the answer…yet. I only know that I had a very successful tank going and happy babies, until I changed the salinity. Within a day or two, all were dead.

So. Next time, I am going to leave them in brackish water and see what happens.

Will there be a next time? Well….I’m fairly certain it’ll happen, especially since Scarlett O’Hara is PREGNANT AGAIN!!!!!!! I noticed that right after I put her back in the main tank, she took to living in the water filter. I thought, no, she can’t be getting ready to have more babies. She JUST delivered. I know that both times now, just before we saw Scarlett carrying around babies, she spent some time on top of or inside of the water filter.

Today, since I’d not seen her out in the main tank AT ALL for days, I pulled the water filter cartridge out and she jumped down into the tank water. I did a double take. SHE IS PREGNANT AGAIN.

In reading up on crab sex, apparently the female can store the sperm for months at a time. So I guess multiple pregnancies can happen even if she doesn’t mate again.

I have decided for this pregnancy to do the “status quo” experiment, ie just leave her in that main tank. I have no idea how far along she is, I have no time to turn the nursery tank around and re-prepare it for another delivery. So this time I am going to leave her in the main tank, which is brackish, leave the water filter on, and if any babies survive, great. If not, no big deal. And it’s the one set of conditions I haven’t tried yet – just leave it all alone and see what happens.

I frankly would be surprised to see babies survive, but, who knows. In the meantime, I will go ahead, clean out the nursery tank, re-establish it with clean brackish water, and I think I will even try that method of “fishless cycling” that the UK website mentioned – ie establish the nitrogen cycle without fish. At the very least, by the next time someone is pregnant again, the tank will be clean, mature, brackish, and ready for another try at this. NOT QUITTING YET!!!

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