Is this a good cray tank?

[knifegill]

Sounds like fun.
Hey, I found a site stating that 72 degrees is a little too warm for NA crays. Should I drop it down to more like 65? What are yours at?

 

[Dark Jester]

Mine are at 70-72. It cools off a couple degrees at night, but stays around 72 with the light on. The heater is set to 70.

Assuming they're related to clarkii they should be able to handle a fairly wide range of temps. Clarkii are found in most of the states, from northern Washington to Florida. I'd put that in the 50-80 range fairly comfortably.

Edit: I'd actually probably just leave them at room temp if I didn't have the guppies in there. That'd be mid 60's.

 

[knifegill]

Without knowing the collection point of the original specimens, the best we can do is see what temperature they breed the fastest at. How about you keep yours at the place it is and I'll drop mine. In a few months we'll compare the time between berries and see how frequently they are reproducing. I will also likely be moving one cray to another tank anyway, so I'll be able to test perhaps 60 degrees as well with that one.

 

[Dark Jester]

Cool, sounds like a plan.

 

[xrayjeeper83]

mine are at 74, guess i need to turn that down some more

 

[knifegill]

Don't know. Still figuring it out for ourselves here. Perfect temp not known. Or is it?! *searches web*

During growth experiments, mortality was lower at 20°C compared to higher (25°, 30°C) or lower temperatures (15°C), and lower under short-day than under long-day conditions

Okay, so what's 20 degrees in fahrenheit?
http://onlinelibrary.wiley.com/doi/10.1002/jez.a.143/abstract

 

[knifegill]

Looks like 68 degrees might be our magic number. Read a few clips about ontology of the crays in question and seems right. I mean, it's a lab. It's what they do.

 

[Chicklette]

I have TONS of hiding spots for my crayfish and lobsters, the more the better. I put in some crushed egg shells about every three weeks. They also benefit from a cuttle bone now and again at the pet store in the bird section, they eat it. Soak it and take off the hard shell.

 

[knifegill]

They eat the whole thing?! Okay. Will provide.

 

[Dark Jester]

http://onlinelibrary.wiley.com/doi/10.1002/jez.a.143/abstract

Nice find, I hadn't seen that paper yet.

Females matured early (at an age of 141–255 d, a cephalothorax length of 14–21.5 mm, and a weight of 0.63–2 g) compared to other crayfish species. Reproductive females with a cephalothorax length of between 25–35 mm produced large clutches (up to 416 eggs) and brooding periods varied between 22 and 42 d.

Guess that proves the marbledcrayfish.com guy doesn't know what he is talking about. They don't hit maturity until the main carapace is 14-21.5mm long. The tail is usually about the same length (maybe a little longer), which would make them start being capable of reproduction at around 1.5" overall. I've read that initial brood sizes are usually in the 30-100 egg range, but according to the above a full grown adult can produce up to 416 eggs at a time. Opposite of the 'ORIGINAL' expert's statement.

Length and weight increments strongly depended on temperature being highest at 30°C, and lowest at 15°C. At 25°C, cephalothorax length and weight increased by 17.5 mm and 1700 mg, respectively, in the course of 150 d, whereas at 15°C these parameters increased by only 7 mm and 100 mg during the same period of time.

68°F might be the best to give the cray the longest life possible, but it looks like heat affects growth rate. If raising them for feeders, you probably want them to bulk up as fast as possible. In that case, you'd want them in the 25°C (77°F) range.

Temperature will also affect hatching times. They list 22-42 days as an incubation time, but don't have the specific temps listed in association with that in the abstract. I'd guess the longer hatch times are at cooler temps.

I'd give 68°-77° F as an ideal range for general care. Lower end if you aren't going for maximum growth rate or brood size, higher end if you want them reproducing and growing faster.

Photoperiod slightly affected growth at 25°C. During growth experiments, mortality was lower at 20°C compared to higher (25°, 30°C) or lower temperatures (15°C), and lower under short-day than under long-day conditions.

Think I might drop my light period from 15 hours/day to 12. Makes sense with crays generally being nocturnal creatures, they probably have less stress overall with a longer night cycle.