How Tough Are These Little Guys?

10-gallon tank started 11/19/14.

10-gallon tank started 11/19/14. 



The tank and the 20″ glass canopy are Tetra products. The undergravel filter and three 5-pound bags of aquarium gravel are Petco products. The Resun lamp — picked up via Craigslist. The fluorescent tube died shortly after purchase, and the replacement is temporary until I can find a better one. The pump, which isn’t visible in the photo, is a Stellar W-60 with twin outputs, one for each of the vertical exhaust tubes. I bought this (and two other models, S-30 and S-10) years ago and don’t see them for sale anymore. The S-10 is on a 2-gallon tank, and the S-30 was on the temp. Both can be seen here. They’re extremely quiet, powerful, and reliable.

In the process of starting this new tank and moving the opae ‘ula from the temporary tank into the new, I carefully removed the sponge filter from the temp to make sure none of the little guys were hitching a ride. I then bailed water, using a small plastic container, from the temp into the new until about an inch remained. I picked up the temp and slowly poured the remainder, with the opae, into the 10-gallon.

I use this bail and pour method because netting isn’t very effective. The opae are quick, and their small size makes them vulnerable to injury caused by the net. Thus, it’s a lot easier to simply pour them from one container into another.

That was last night. I had left the sponge filter and the temp tank on the counter next to the sink to dry. This morning, when I ran the sponge filter under the faucet, an opae washed out and landed on the sink floor. I quickly placed my hand between the drain and the opae to keep it from washing into the drain. When I lifted my hand to see if I had saved it, I found it clinging to the edge of my index finger. If it hadn’t, I had no idea how I’d pick it up.

I opened the glass canopy on the 10-gallon and flicked the opae in. When I looked to see if it was alright, I couldn’t distinguish it from the others and assumed it was. About an hour later, when I lifted the canopy hatch, I found the opae stuck to the bottom of the hatch, trapped in a water droplet and held there by the surface tension. I quickly splashed some water from the tank onto the droplet to wash it into the tank.

Again, when I looked in to see if it had survived the ordeal, I couldn’t distinguish it from the others so assumed it had. I made sure to check to see if any bodies were floating around or lying on the tank floor. Negative.

So, how tough are these little guys? If this survivor is any indication, then s/he survived out of the water for at least 10 hours. I didn’t see her on the surfaces of the sponge filter so she much have somehow gotten inside. How, I’m not sure because there are no visible openings anywhere. If she was inside, then the small amount of moisture remaining in the sponge must have kept her hydrated.

She survived a drenching in tap water and a landing on a sink floor that must’ve had some detergent residue. She had the survival instinct to cling to my finger. When I flicked her into the 10-gallon, I inadvertently sent her flying onto the bottom of the canopy hatch, where she remained trapped in a water droplet for another hour or so.

If I don’t see her corpse on the tank floor in the coming days and weeks, then I’ll know she survived the ordeal.

Now that’s tough.

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4 Responses to How Tough Are These Little Guys?

  1. jhamkins says:

    I love your blog! I have about 70 opae ula in a 12 gallon Fluval tank, for about a month or two now. I have a hang-over-the-edge filter pump, which I usually run on low during the day only, but I think it would help the water cleanliness to run it on high, since I can see that there is a large accumulation of droppings on the tank bottom (I have no gravel substrate, but I do have a large number of red volcanic rocks that are now covered with algae). But I fear that the little opae ula might be harmed by having fast moving water in the tank, and they do seem disoriented when caught in the incoming flow of the current set-up, although I don’t think I’ve killed any yet. I noticed in your videos that the flow level seems to be quite high, with a lot of stuff floating around vigorously. Do you think it is a problem to have a higher water flow in the tank? Have you ever thought that opae ula were harmed by having a high water flow? Do you have any recommendations for minimizing any negative impacts of higher water intake through my filter system?

    Do you run the filter system when there are hatchlings in the tank? I don’t yet have any berried opae ula, although I am hopeful, since I think my set-up could accommodate a large number if they should reproduce. My plan was that when I started seeing young, then I would shut the filter system down or severely curtail it. Is that a good idea? Right now, my only precaution is a shrimp guard over the intake, which definitely prevents any opae ula getting sucked in.

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    • jhamkins says:

      I just found my first berried opae ula! She has four or five eggs, and I have many others that seem to have eggs still inside them, but not yet carrying them; but I cannot be sure. So I’ve got to decide whether or when to shut off my filter for fear of hurting the young’ns.

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      • JimS says:

        Hi jhamkins. Please see Opae’ula Larvae in My 10-gallon Tank for my reply. -Jim

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      • JimS says:

        jhamkins, my apologies. I’m reading your messages out of sequence. I just saw this message re your first berried female a few minutes ago. Congratulations! This is the point at which it gets really interesting. Please disregard my last message re experimenting with the power level and duration of your filter. The old adage, “If it ain’t broke, don’t fix it,” might apply here. Present conditions have started the breeding process, so you may want to just stay the course and continue what you’ve been doing. Probably the worst thing to do right now is to alter the environment. These little guys seem to adapt to their environment, and any radical shift in their routine might be upsetting. For example, I think we’ve all learned that if you move a rock or structure in the tank, they stay clear of it for a few days. I recently redid the coral mound in the 5-gallon on my desk — replacing the smaller coral pieces with larger ones — and most of the colony remained outside, refusing to enter it for several days. My guess is it’s a survival mechanism. -Jim

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