Opae’ula are fun to raise. Since they don’t need much space for a simulated natural environment, we can be creative in building tanks. I believe a gallon jar is about the smallest optimal size. At a thrift shop, I found a 1-gallon glass jar (see photo above) with a lid and decided to turn it into an opae’ula tank.
Since there’s no opening for an air line, I raised the lid at one end about a quarter of an inch to insert a line. Since the lid is made of glass and a bit heavy, I added two rubber shims on both sides of the line to prevent the lid from crimping it. I made the shims out of two quarter-inch wide rings cut off from the end of a large plastic hose. Cutting through the ring at one point creates a u-shaped shim that will fit over the bottle edge.
The tank is not quite ready for opae. Thus far, I made a UGF out of a plastic cover (see photo below of a similar cover) and a spare plastic tube, covered it with gravel, inserted an air line into the exhaust tube, and added brackish water from one of my established tanks. I’ll be adding a coral substrate over the gravel next before adding a small colony of opae from the 18-gallon.
The cap that I actually used was slightly wider than the one in the photo. Find a cap size that will fit in your tank, leaving about a half-inch to an inch between the outer edges of the cap and the interior wall of the tank. Using a Dremel tool and a small bit, I drilled tiny holes in the cap and on the outer edges of the cap. The holes were approximately an eighth-inch apart from one another.
I then drilled a larger hole, toward the edge of the cap, that’s a hair narrower than the diameter of the exhaust tube. This is to make sure that the tube will stay in place when inserted. I then worked the tube into the large hole so that it was about half way between the top of the cap and the bottom of the tank.
After inserting the UGF in the tank, I added a gravel substrate that covers the UGF by about three-quarters of an inch. I added brackish water from the established 18-gallon tank, ran an air line down the exhaust tube, adjusted the air flow with check valves in the lines attached to the air pump that’s shared with the oblong 1.5 gallon tank.
I’ll be adding coral to the habitat this coming week. I’ll also be adding some opae.
See the follow-up article: Glass Jar with Lid: New Opae’ula Tank