18-gallon Opaeula Tank – Video 8 April 2019

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4 Responses to 18-gallon Opaeula Tank – Video 8 April 2019

  1. Christina says:

    Aloha! I’m glad I found your blog. Your tanks are really flourishing, the Opae ‘Ula look very happy. I just started my 2.5 Gal tank (bought at Kahala Petland) about a few days ago, and I got white sand collected from Sand Island (washed it like rice till clean lol) and small lava rock from Petco Beretania (I want more small ones!) . I was thinking of using seawater from Sand Island but it smelled really bad. Instead I’m using the Instant Ocean with half Pür filtered tap. Currently it’s facing the ocean side window, but doesn’t receive a lot of direct sun. So I just got a desk lamp for now, to start some algae growth. I’m hoping the ‘live’ sand which I collected won’t have too much bad bacteria in it, and will provide necessary calcium for Opae. I like the look of lots of lava rocks like their natural habitat. I’ll probably wait a few weeks until my friend will be giving some of her Opae ‘Ula! I’m so excited. My husband calls them tiny ocean insects haha. My house can get up to 86 degrees when its hot and humid though…(Summer coming soon..) Do you ever worry about the temp for your Opae as well? Looking forward to seeing more of your project, you’re an inspiration 🙂


    • JimS says:

      Thanks, Christina, for the kind words. I got my inspiration from all the others who have been publishing and posting about these little opae in YouTube and elsewhere. About tank placement: I live in an apartment with only two window directions, south (Diamond Head) and west (Ewa). I didn’t have much success facing west. South has been ideal.

      I also found that direct sunlight for long periods may not be a good idea. Indirect sunlight and maybe an hour, at most, of direct sunlight a day may be optimum, but ymmv. Sunlight varies according to seasons even in Hawaii. I haven’t had temperature problems and haven’t used a thermometer. Opae seem to like “short” bursts of sun-induced heat and thrive on the new algae growth. “Short” might mean 30 minutes to a couple hours. Monitor your tank for optimum sun/heat. Imagine what the conditions must have been like in their natural habitat, and try to simulate it.

      About algae growth: Be prepared for some weird stages while the algae settles into a sustainable ecosystem. This is probably the toughest part of setting up an opaeula tank. Expect to make mistakes until you get it right.

      Don’t panic if the first sign of algae is a brown or red growth all over the tank. This is a preliminary stage. This will be followed by rich growth of green algae. Both these stages may be overwhelming the tank. The brown will disappear on its own. You may need to remove some of the green overgrowth. The tank will reach an equilibrium at some point where you won’t have to do much to clean the tank. The opae will eat the algae and keep the glass clean.

      I had bad luck with beach shell fragments and ocean water. To clean the tiny shell pieces for substrata use, I boiled it. But I found that the opae could easily bore through the layer to get to the UGF reservoir below. I got the seawater from Ala Moana Beach, so it was probably contaminated. The opae got sick, so I replaced the water with aquarium salt and tap water that I left standing for 24 hours to get rid of chlorine.

      After placing the opae in your tank with beach sand, monitor them closely for at least a week. If they remain active, then the sand is fine. If they gradually become lethargic, the sand (or the lava rocks?) may be contaminated.

      If you’re using a UGF (under-gravel filter) system, the sand will leak down into the reservoir at the bottom. You’ll need to add a layer of gravel on the reservoir surface that will keep the sand from falling through. If you’re not using a UGF, then you won’t have this problem.

      You can judge the health of your tank by simply monitoring the opae activity level. These little guys, when healthy, are always busy, grazing, swimming around, exploring. This is what makes them fun to watch. Btw, this is day and night, even when it’s dark. If they aren’t and try to remain hidden, then there’s something wrong.

      The ultimate sign of a healthy tank is reproduction. When they begin to breed, you know you’ve reached a sustainable level.

      Trying to figure out what’s wrong and solving problems is part of the opaeula experience. It took me at least two years to finally achieve adequate sustainability, where maintenance is almost zero. Have fun and enjoy this hobby! -Jim


      • Christina says:

        Thank you so much for the tips! I’m not using a under gravel filter, but ill keep that tip in mind if I plan to use one. I moved my tank facing my lanai now, which gets indirect sunlight off and on throughout the day. I will wait for the algae to transform to green before I put my shrimp in. So far its been less than a week, so I dont really see much growing. I didnt boil the sand or lava rock before putting it in, only rinsed it well with filtered water. I’ll probably start boiling the newer affitional rocks, or if the opae look lethargic ill redo it all. How is your 18 gallon doing?


        • JimS says:

          You have a thoughtful plan that allows for contingencies and a Plan B, and that’s the key and fun of this hobby: experimenting, monitoring, adjusting, etc. Opaeula are hardy and can tolerate a wide range of conditions, so as long as you monitor them and make changes when needed, you’ll be fine and your tank will eventually reach a sustainable level. I’ve lost count of the number of tanks I’ve completely overhauled, and the opae survived them all.

          My 18-gallon (filled to the 10-gallon level to control for salt creep) is in a steady-state right now. Since the population includes opae from a 10-gallon that I decommissioned, very little breeding is going on. The population is too large. Still, the opae are active 24/7.

          The only maintenance for the last year or more: (1) topping off the water level that slowly drops from evaporation, (2) turning on the UGF a few times a week for about an hour or two, (3) dropping a few tiny chips of algae wafer into the tank for a treat every few weeks or so. They swarm the chips. Fun to watch. A wafer is about the size of a dime, and one will last about a year as I slowly cut chips off for the tank.

          I haven’t had to clean the tank glass. The water is always crystal clear. When I turn the UGF on, there’s a light clouding at first, but it disappears quickly.

          About algae growth: If you find that nothing’s happening, you may need to raise the bacteria level by adding water from a long-standing healthy opae tank or adding a few opae to the tank.


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