Oxygenation requirements

[towawayzone]

I have literally checked out every page of this forum (lol) and I am obsessed with these shrimp. But I haven't seen any posts specifically dedicated to oxygen. I have seen posts that discourage a tight fitting lid, but no more detail. Is a cork lid okay? Is a mason jar with a lid okay? I have a reef tank that is rimless with a netted lid, so I know how quickly evaporation occurs and I'd like to have something that totally covers the top.

[sliphorn]

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Punch some holes in the mason jar lid and you are good to go.

[Tiny Ocean]

If you have the very simple set-up that Mustafa recommends -- a mature tank containing a good healthy mass of his Chaeto alga, calcium-rich shell or coral sand, and the little MTS (Malaysian trumpet snails) -- then you can have a lid that covers the tank with just a few inches of air over the surface of the water. A flat piece of glass, or something of the sort which allows little evaporation, is fine. Just open it when you feed the shrimp every month or so, and top off the tank with distilled water now and then to replace any loss from evaporation. (You need to know where the proper water level is, so mark it when you first set up your tank. The level will change as you add rocks and stuff so make sure you mark the correct level with and without ornaments.)

(By the way, don't top off the water by just pouring pure distilled water rapidly into the tank. The glob of water might reach the bottom of the tank and hit the shrimp before it is well mixed with the salty water. Pure distilled water is caustic to organisms that are adapted to mineralized and salty water. Instead, trickle it slowly slowly down a chopstick or fork while gently swishing the object over the water surface, so that the distilled water mixes well with the brackish water. Swish only the surface. Don't roil the shrimp around.)

You will know your tank is mature -- meaning, you have a proper community of microorganisms built up -- when your water tests for ammonia and nitrites are consistently zero, nitrates are very low and consistent, and pH is consistent when you measure it first thing in the morning. (pH changes slightly throughout the day as the Chaeto takes out acidifying CO2 from the water in response to light intensity, which varies from day to day. Checking pH first thing in the morning after the tank has been dark all night gives you the most consistent circumstances for testing.)

When a tank is mature, it has a diverse set of microorganisms that can rapidly break down the wastes of the shrimp and snails, providing nutrients for the Chaeto. If you have enough Chaeto, it provides enough O2 for the shrimp, snails, and oxygen-using microorganisms. The shell or coral sand keeps the water from acidifying from the CO2 outputs of respiration from the organisms. If the sand is half an inch to an inch deep, that's plenty to provide habitat for the substrate bacteria.

If things get out of whack so that oxygen levels in the water drop too much, you'll see the MTS snails constantly hanging out near the surface of the water where the oxygen content is highest. When oxygen levels are okay they will still do this at night, but not all the time.

Opae Ula produce a very low bio load. That's what makes it possible to have a beautiful display of dozens of them in just a gallon tank. The snails are also fairly low bio load because they are tiny. If you feed too much, the snails can overpopulate, requiring too much oxygen and putting out too much waste product. But if you don't throw things out of whack by having a tank floor covered in snails, the gases work out fine even if the tank is sealed. That's how the infamous "Ecospheres" kept shrimp alive so long (mine was over 13 years old when I opened it). Of course we don't want such poor conditions for our opae ula -- we don't want them just barely and perhaps miserably hanging on to life, we want them to thrive. Opening the tank cover now and then and providing a little tiny bit of food is sufficient to keep them quite well.

Adding bigger snails, or fish, or plants that struggle to survive in brackish water and keep dropping bits of dead material...that's outside Mustafa's model. Much greater risk of things going haywire, including oxygen depletion, ammonia, etc.

[Tiny Ocean]

Ooof, please forgive the overexplaining above. I failed to absorb the fact that you already operate a reef tank, which means you already know way more aquarium biochemistry than I do. . I will leave the post up in case it might help someone else though.