30gal Opae tank?

[Fishkeeper]

I'm going to get a heater, and just for insurance, I'm also getting one of those shutoff probe things that turns off whatever is plugged in if it gets past a certain temperature range. That way, if it fails, it'll fail in the direction that results in chilled shrimp and not cooked shrimp.

Even if they don't need a heater to breed, the heat will definitely speed up their breeding. Warmer water means warmer shrimp bodies, which means faster shrimp metabolisms, which means faster breeding and growing. Which, given that I hope to eventually have a couple thousand shrimp in this tank (and I know that'll take a long time), is ideal.

[Mustafa]

Mustafa said he had breeding in tanks that he kept outside in San Diego where the low temperature was 39 degrees! These are some hardy shrimp indeed.

Just to give it a bit of context, the shrimp were breeding before it was that cold and the larvae were still floating when it got colder. Also, keep in mind that temps in socal don't stay that low. The days will still be in the 60s at least in the winter. The 39 mentioned above is basically the low of the day for only about an hour or two at most and then the temperature rapidly rises. And 30s are still pretty rare during most winters where I live. 40s are about as low as the low for the day gets on most winter days. The above mentioned tank was a 10 gallon tank so it adjusted to the outside temperature rather quickly. It's definitely not ideal though. Nowhere near....

[Mustafa]

I had an outside tank that had it's heater accidently unplugged for a few days. All the opae were on their side on the bottom. Not moving. I could tell btthey were still alive so I plugged the heater back in and within 5-6 hours they were swimming once again. No deaths. I doubt that the opae would breed in Southern Ca in the winter, still too cold.

That's because the temperature dropped rather suddenly. If the shrimp are out there and have time to adjust to the lower temps gradually with the changing season, then they won't drop on their sides and almost die. They will actually even continue picking at the biofilm until about the mid to higher 40s, just a lot more slowly...like slow-motion picking. At lower temps they just sit there and you can tell they are just waiting and "hoping" for better times.

Another extreme temp sidenote...on the high end they can take temps to about 102F for a short time. At 104F they start dying. You'll see that they are not feeling too happy in the upper 90s because instead of picking really quickly at the substrate, they start swimming around the tank. (And no, I did not raise the temps that much on purpose.)