I began a new opae’ula tank over the weekend, making use of an old 18-gallon that I once used for tropical fish. I transferred the small opae’ula colony in the 2.5-gallon tank to the new tank. My sense is that 2.5 gallons is too small, and 5 gallons may be the minimum for breeding. The 18-gallon is also an experiment to see if I can better control the problem of salt crystallizing on and around the tank. The tank is filled to about the 10-gallon mark. The remainder creates, I hope, a large enough buffer between the water surface and the top of the tank, which is covered with a Tetra glass canopy. The only openings are on the rear corners, small slits to accommodate the air tubing. The buffer, I’m hoping, will keep the splash and evaporation within the tank and keep the top and sides relatively dry and free from salt crystals. The air pump is an Aqua Clear 30 with double outlets, one for each of the two exhaust tubes. In Honolulu, I haven’t found a better pump. I have an Aqua Clear 5 for my desktop 5-gallon tank. The air flow is powerful and steady, and it’s absolutely silent. It vibrates, but it’s not noticeable. It also stays in one spot.
The opae’ula in the 5-gallon Fluval Chi have begun breeding. Tiny juveniles began appearing about a week ago, but I didn’t see berried females or zoeae prior to that. I now see at least one berried female, so the breeding is ongoing. Not sure if it’s just coincidence, but the breeding seems to have begun after I removed the sponge filter and went with the undergravel filter, which remains on all the time. In this tank and the 18-gallon below, I added capsule filters to the exhaust mouth to slow the outflow, which might have been too strong.