Breeding Opae’ula in a One-Gallon Tank

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5 Responses to Breeding Opae’ula in a One-Gallon Tank

  1. Diane Fernandez says:

    Mahalo for all the information you provided and share. Look forward to future posts


    • JimS says:

      Hi, Diane. My apologies for the long delay in responding. I’ve been busy with work and haven’t been logging in regularly. You’re welcome, and I’m glad I’ve been of some help. I really enjoy these little guys! The fact that they’re part of our Islands makes this hobby even more meaningful. I hope the state will be able to preserve the remaining opae-ula colonies in existing anchialine pools. By spreading this hobby and interest, we can all do a small part in preserving them for future generations. Aloha, Jim


  2. CH says:

    Hi Jim!
    I started reading your blog last year (2016…I went back and read all of your previous posts too) as a means to plan out my own Opae ‘Ula tank. I wanted something small that would fit on my desk at work, wouldn’t require too much maintenance, and would be different from what other people had.
    I read and watched all the resources I could find about Opae ‘Ula; the videos by Christine Ha, the Fukubonsai, (Odin),, websites and other websites that gave generic information regarding brackish environments, even the DLNR website on anchialine pools. It’s been a long journey, but I think my tank and colony are doing well. Your insights have helped me to better understand what works to keep these shrimp happy.
    I have a few questions regarding water quality that I’m hoping you can help me with.
    Without getting too verbose, this is what my water parameters are:
    pH: 7.8
    Ammonia = 0
    Nitrite = 0
    Nitrate = 80
    GH: off the charts (we’re talking 300 +, the tds meter gave a number and said “x10”)
    KH = 53.7
    Salinity = 1.004

    Here are my questions:
    How can I lower nitrate levels without having to do regular water changes?
    Are those GH levels bad for Opae? If yes, how can I lower them without affecting the pH buffering capabilities of the water?

    Any insight you may have would be greatly appreciated!


    • JimS says:

      Hi, Cheryl. Welcome aboard the opae-ula ship! They’re fun to care for and observe. They’re lively little guys.

      I stopped checking water quality levels with test strips long ago.

      I’m not sure what kind of biological/mechanical filtration you’re using, but I think you’ll need both. The key is rate of flow. Nearly all pumps are designed for fish — not opae. The flow is too strong for opae. When it’s too strong, it filters out both good and bad bacteria. The flow has to be slow enough so that the tank retains a high level of good bacteria. The flow doesn’t have to be very strong to remove the bad bacteria.

      If you’re using a UGF system, then you have a biological filter. But the UGF alone isn’t enough. The bad bacteria remains in the tank and gradually increases. A sign that this is happening is decrease in opae activity. They’re naturally very active, grazing and swimming about all day and all night, too. If they’re not active, the water’s bad. Another sign is poor algae growth in the tank. What remains is a kind of brown sludge. The tank begins to look like a dead zone.

      Frequent water changes to revive the tank might work, but the problem is that the new water doesn’t contain good bacteria — and the good bacteria in the tank is depleted. Good bacteria takes times to grow in a tank.

      Water returning to the tank ought to go through a mechanical filter of some kind before re-entering the tank. In this case, carbon or some sort of filtering mesh should do ok. If the rate is slow, then the level of good bacteria in the tank will remain stable.

      Tank placement is also critical. They need natural sunlight. I’m finding that the light should not be direct for long periods of time. I have two small and one medium tank in the living room with windows facing west. The tanks are in the middle (off to the side) and end of the room. They get indirect sunlight in mid- and late-afternoon. This seems to be just about right.

      Tanks that I had placed very close to the west windows didn’t fare very well over time.

      I have one medium-sized tank in a bedroom with south-facing windows. It’s about three feet away from the window, so it doesn’t get too much direct sunlight. But it does get a lot of indirect light all day long.

      I haven’t changed the water in my tanks for quite a while. I simply top off with bottled or tap water. I’ve been experimenting with tap water (left in an open container overnight to release chlorine gas — the water in my area has no other chemicals) in two of my tanks, and they’re doing fine. My plan is to switch all tanks to tap water in the next few months.

      As long as the opae are active and show signs of breeding, I know that the water quality is fine.

      Apologies for this long rambling response. I hope this all makes sense. Please keep us posted on your experiments with your tank. -Jim


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