Updated 3/4/16, 7/21/18
I’m setting up a 1-gallon opae’ula tank in a glass jar I found at a thrift shop. This tank is about half done. It shares an air pump with the oblong 1.5-gallon tank that’s partially visible in the background. Update 8/14/18: For the latest on this tank, click here.
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.
A plastic cap from a throw-away bottle that’s similar to the one I used.
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
Updated article: DIY UGF for 1-Gallon Tank
Opae'ula 
Love it. Can’t wait to see them swimming around.
Ann
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Hi Ann. Busy with work so progressing slowly. The water turned a bit cloudy so I did a 70% water change. Clear now. Added a “seed” coral from the 10-gallon. It’s a piece of coral with green algae growth. I’ll be adding “new” coral by the end of this week and a few opae’ula over the weekend if all seems well. I doubled up on the shims to further reduce the crimping on the air line. The air flow is better now.
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It sounds exciting. Work does interfere with the fun things. Sounds like you’re progressing wonderfully.
Ann
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Finally found some time this afternoon to insert the coral and some opae’ula. These little guys make it fun with their constant activity.
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Looks nice! May I ask why you have a filter?
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Hi Odin. Good question. I’d actually prefer doing without a filter, but from what I’ve gathered thus far, in small tanks (1.0-1.5-gallon) without mechanical filters, opae’ula don’t breed. If anyone has information to the contrary, I’d like to hear about it — with details to allow the rest of us to replicate the setup. In the meantime, I know that opae in my larger (>5 gallon) tanks are breeding, and these use UGF. I’m also aware that hobbyist Nakashima has had tremendous success with larger tanks with no mechanical filtration. But he reported waiting a year before breeding began, and I don’t want to wait that long. Furthermore, his situation is unique. He has access to clean seawater and uses it, diluted with tap water, instead of the usual store-bought alternatives. Btw, he uses a UGF with powerhead in some of his tanks. You’re correct in questioning the use of artificial filtration. For me, this is a final hurdle. If we, opae’ula hobbyists, can prove that mechanical filters aren’t necessary, we’re home. Thanks for asking.
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Enjoying your post. I have a 1.5 glass jar also. Like wise have a filter. I notice a big change, they are more active then ever. I notice their color have deepen also.
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Active and deeper coloring — these are signs of good health. Any signs of berried females yet?
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No JimS not yet my goal is to keep them alive any berried females considered a great bonus. C Set this tank up about five months ago. I’m totally hooked now, just put together a 10 gallon three weeks ago. My mistake 1.5 gallon turns out its 2.5. It looks tiny next to my new half moon tank.
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Hi Di. That seems to be the norm — begin with a small tank, become hooked, and move up to a bigger tank. Happened to me, too. Lol! You’ll get a lot more out of the 10-gallon. The larger environment is closer to natural and encourages more activity. After seeing some success with my larger tanks (10-gallons), I find myself returning to the challenge of smaller tanks to see if lessons learned with the larger can transfer to the smaller. Is a half-moon tank like a bowl? -Jim
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It might sound crazy, but I don’t want them to breed. I don’t have the room or mobility to supply larger and larger tanks. If they can stay healthy without filtration and not breed , it would be great.
Ann
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Hi, Ann. Not crazy at all. I agree with you. I live in a condo where big tanks are out of the question. Ten-gallon is about the max allowed. Re breeding, I’m guessing that opae’ula, like most natural colonies, will breed in response to their environment. The amount of space, food supply, and water quality will dictate whether or not they’ll breed and the frequency. In other words, if they do breed, they’ll probably do so at a pace that will sustain a balanced ecology. Once they reach that balance, they’ll stop. I’m also guessing that when your opae do breed, they’ll do so only to the extent that your tank ecology allows. I doubt they’ll overbreed — unless you’re artificially increasing their food supply. I’m with you re sustaining a healthy colony and not simply multiplying the numbers. The other side of the coin is that if they don’t breed, the colony will gradually shrink. Based on these assumptions, I understock my new tanks to encourage breeding. I don’t do this to simply have more opae. I do it to determine the health of the environment I’ve created. If they breed, then it’s a good sign that the environment is healthy. Also, breeding will sustain the colony indefinitely, with younger ones replacing the ones that die of old age. These are just assumptions. Thanks for sharing. -Jim
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I have a question. When you say SHRINK, do you mean their colony numbers or their body mass? Thanks for having the patience to answer my elementary questions. 🙂
Ann
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Hi Ann. I’m a novice myself, too, and have more questions than answers, so I’m in the same boat. Please don’t hesitate to ask away. If I can’t answer the questions or if my answers are off the mark, someone, hopefully, will speak up and set us straight. Re “shrink,” I was referring to population, but it also applies to the process of slow starvation due to illness or lack of food. It seems they shed their exoskeletons in either direction, as they grow or shrink. -Jim
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As a novice, you are really adding to my knowledge.:-) Thank you for your answer.I’m enjoying your blog immensely.
Ann
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Hi Jim,
These are good extrapolations. This makes good sense. Thank you for your comments.
Ann
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“Extrapolations” hits the mark. With so many unknowns, we end up making a lot of leaps and guesses based on shaky assumptions. It’s a wonder these little guys can survive our craziness. Maybe that’s one of the reasons we’re drawn to them. They’re tough and seem to adapt to and tolerate our whims and experiments. Hopefully we’ll gradually learn how to sustain them in good health for many, many years.
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Amen to that. I love these little guys.
Ann
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Aloha JimS, think of a round cylender cut in half width wise with no obstructions, no corners from end to end.
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Hi
Can you post photos of how the tube going under the UGF plate looks like.
Is it connected to an air stone? Is the air pushing water up evenly or there are dead spots?
Thanks
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Hi, Angel. I don’t have any photos of the action under the gravel, so I created a simple drawing to illustrate what it looks like. I hope it helps. If you have any more questions, please don’t hesitate to ask. As you can see, I don’t use an airstone. But you could if you wanted to. The “dead spots” (gravel that’s not doing any filtering?) are along the outer edges of the cover. A solution is to drill holes on the outer edge, too. My guess is that the UGF creates enough of a vacuum to suck water from gravel throughout the stratum. If by “dead spots” you mean debris remaining in the uplift tube — no, the bubble action lifts all the water back into the tank. In fact, when opaeula (especially the newborns and juveniles) somehow find their way into the undergravel chamber and into the uplift tube when the pump is turned off, they come flying out of the tube when the pump is turned on. It almost seems as though it’s a game for them. -Jim
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Hi Jim,
Thanks for UGF diagram, it clears things up since I was going to stick the airstone down into
the bottom of the tank. I hope airstone works, rigid tube by itself creates I guess a more annoying noise. So this method, the water is going down through the substrate and back through the uplift tube?
Can the top of the tube remain in the water for less noise?
How would I know what is too much bubble or not enough?
Thanks 🙂
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Hi, Angel. The problem with an airstone is that it creates a fine mist that gradually builds salt creep around the edges of the tank. Re noise from a rigid tube: I didn’t find that a problem, but YMMV.
Yes re water seeping through the substrate, into the undergravel chamber, and back into the tank via the uplift tube. A “natural” organic filtering system.
Yes, the top of the tube can be below the waterline. The only reason to keep it above is to keep the opae from crawling down into the chamber below when or if the pump is turned off. I leave the pump on for about an hour a day. It’s off the rest of the time. Opae that somehow get into the chamber or inside the tube are quickly flushed back out when the pump is turned on. -Jim
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Hi Jim,
Good to know! I thought you kept pump running 24/7. I could try without airstone and
see how it goes. More than an hour with pump on is too much stress for shrimp?
I am setting mine up next week. Waiting for the grate material.
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Hi, Angel. I used to keep it running 24/7, but decided the current was too strong. I’ve been experimenting with shorter durations and found that an hour a day is just about right for the bigger tanks. (I use a low-power pump system for my smaller tanks and keep those on 24/7.) Duration depends on the size of the tank and the effect on the opaeula. They generally prefer very low levels of agitation. But tide surges occur in their natural habitats, so I think an hour may be about right. But you’ll need to observe and experiment to set the best duration. I’m looking forward to hearing about your observations and experiences when the tank is set up. -Jim
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Hi Jim,
I see. I will being using air valve to adjust. I guess if not enough air, then it will not push water through substrate either. I just glued the tubing to the gravel plate. I will keep you posted. Makes sense what you said, run it long enough to maintain clean water but not too stressing shrimp. Thanks 🙂
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Hi Jim,
Some feedback. If anyone is attempting this, you must be very careful in using small substrate
where it will cover the entire area of the UGF plate, leaving no openings. My lava rocks were larger pieces so I had some opening in the corner of the up lift tube. The opae got stuck underneath the UGF and could not get back up. I had to remove the lava rocks and leave an opening so they can get back up to the top. Unfortunately, this now causes the shrimp to go from the bottom and get stuck in the uplift tube. Shrimp is stuck there while the air is on.
These little guys are super fast. If you know of an easy quick way to get them out of the tank, please let me know. I would like to redo the UGF but taking the shrimp out is even more challenging.
Thanks
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Good feedback, Angel. There shouldn’t be a problem with water getting through the gravel and into the UGF chamber. The issue is the openings in the UGF. If they’re too large, gravel will get into the chamber.
I learned to not worry about the opae somehow finding their way into the UGF chamber. The juveniles are especially prone to do this because of their tiny size. Re flushing them out: in my case, I just turn on the air pump and they come flying out of the uplift tube. If this doesn’t work for you, remove the airstone, i.e., if you’re using one.
You bring up an interesting problem re making major changes, such as redoing the UGF setup. The problem becomes very complicated when there are juveniles or larvae. They are almost microscopic, so you won’t be able to catch them all. They’ll easily dig into the substrate, making it impossible to find them.
The few times that I’ve had to do this, I simply made the changes with the opae in the tank. For example, to repair one of the uptake tubes, I gently moved the gravel away from the area and heaped it around the exposed surface of the UGF. I then worked on removing and replacing the tube. After I was done, I gently swept the gravel back over the area.
Did I crush any opae? I might’ve, but I’ve reached the point where I trust that they’re smart and quick enough to avoid being buried or crushed. They’re a lot tougher than we think they are. When they realize you’re working on an area, they’ll steer clear.
I once had to move almost the entire coral “condominium” to, again, work on the uptake tube. I gently picked up the coral chunks one at a time and moved them elsewhere in the tank. I didn’t want to take them out of the tank for fear that opae would be clinging to or hiding in the coral. After moving the coral, I swept away the gravel and worked on the uptake tube problem. The opae stayed away. After I was done, I reversed the process.
Doing any kind of work in the gravel will loosen the waste material caught in the substrate, turning the water murky. However, the particles are actually quite clean, and running the pump for a half hour to an hour will turn the water crystal clear again.
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Hi Jim,
How do I check if UGF is working correctly? Like if water is pushing down from uplift or being pushed up from under UGF, or if it is working at all?
I had spare tank. I setup again with UGF and used fine black sand first, then some lava rock on edges. Opae should not be able to go under the UGF now.
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Hi, Angel. You’ll know the UGF is working properly — water flowing up the uptake tube and back into the tank — if water or bubbles are flowing out of the exhaust on top. You’ll know if the pump is pushing water up through the substrate via the bubbles coming out of different areas in the substrate. If the latter is happening, raising the airline a little higher in the uptake tube should solve the problem.
The problem with fine black sand as the first layer on the UGF is that the grains may fall through the openings in the filter and eventually fill up the chamber below. If anything, a layer of gravel slightly larger than the opening should be the first layer, followed by fine-grain sand. The gravel will keep the sand out of the chamber. I haven’t tried fine sand, assuming that it may not work as well as a biological filter. -Jim
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