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Sterilizing a crayfish (marmorkrebs) tank


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#1 Guest_gzeiger_*

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Posted 06 May 2011 - 02:24 PM

I'm packing up to move in the next few days, and I've started to take apart my tanks. In doing so, I found a number of marmorkrebs, the parthenogenic demon crayfish, in a 50 gallon sump tank. I had been raising them as feeders in another tank, and although at one time I had placed one in this sump I had thought them eradicated. I found young ranging from about 2mm to an adult of 1.25 inches carrying eggs. I believe I sterilized that tub with about 3/4 of a quart of ammonia, but having picked through the rock that was in it I found that I had missed several when I went through the first time picking them out by hand.

So now I have this 30 gallon tank, mostly drained, which I had thought contained only a handful of adult crays, but I'm finding at least two broods of young also. What is the recommended method for sterilizing the remaining contents of the tank? I intend to dump the substrate - lava rock and crushed oyster shell - in my yard. It's far from water, but it's been raining lately and I don't know how far a cray could travel over land.

#2 Michael Wolfe

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Posted 06 May 2011 - 02:59 PM

Put the substrate in as many 5 gallon buckets as it takes... drive them to my house... or the convention in Virginia... and I will dump it into an aquarium full of hungry chubs (now there is a redundancy... "hungry chubs"). I predict there will be no survivors. I would think that madtoms would also work and maybe even sunfish... but I like chubs.

Heck, if you bring it to the convention, you might could even donate it as an auction item... generate revenue for NANFA! Live food starter culture...

...to actually answer your question I would think that two gallons of bleach and enough water to cover the substrate would really kill anything...
Either write something worth reading or do something worth writing. - Benjamin Franklin

#3 Guest_gzeiger_*

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Posted 06 May 2011 - 04:01 PM

I have a tank of hungry bass and catfish right here. But I would already have predicted no survivors in such a small tank that until today had contained 4 adult crayfish, 3 young bullheads and a pickerel, but I found some that are definitely at least 2 months old, based on their size.

#4 Guest_Newt_*

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Posted 06 May 2011 - 06:38 PM

Bleach kills everything, and volatilizes away without residue.

#5 Guest_schambers_*

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Posted 07 May 2011 - 05:20 PM

Alternatives would be allowing the substrate to dry out or setting up the tank and putting in some fish to eat the young crays. Putting some fish in the tank to eat them has the advantage of preserving the bacteria in the substrate.

#6 Guest_gzeiger_*

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Posted 07 May 2011 - 06:52 PM

The substrate is getting thrown away rather than try to transport it 3000 miles, so I don't care about bacteria. If I were bringing it with me, I could control it and wouldn't worry about sterilizing it.

As a word of caution to anyone else keeping these things, predation by fish is evidently fairly ineffective at eradicating them. I ended up finding them in three places. I had a 30 gallon tank which had been breeding them for about a year. This tank has also housed three brown bullheads, which love to eat crayfish, for the last four months. I had seen no sign of babies in a long time (since before the catfish were added). When I took the tank apart I ended up finding 15 or so young, again of two different age groups, and after applying half a gallon of bleach diluted about 50% by the remaining water I again found a half dozen dead that I had missed in two rounds of manual removal.

The sump tank mentioned in the first post was the filter for a 75 gallon tank which housed a young smallmouth bass, a fat sleeper goby, a couple sunfish and a large native cray. When I add small crays to this tank, the bass will eat 6 or more immediately, and all these fish so I assumed that after a few days there would be no survivors. This seems to be the case for wild-caught ones which I would add by the dozens periodically. Upon disassembly I found only the one 3.5" adult native I had known about (an escaped feeder who eventually grew too large and had been in the tank six months or more) and 8 marmorkrebs. I hadn't added any marmorkrebs as feeders in about a month. I see no evidence of a second generation in this tank at least, but three of them appeared (based on size; I don't know how else to tell) to be sexually mature.

#7 Guest_schambers_*

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Posted 08 May 2011 - 04:52 PM

Adult marmorkrebs are very adept at hiding while they are in berry, if there are any hiding places or gravel to dig into, you will never run out as long as the adults remain in a tank. They will also occasionally move into other aquariums, even crossing several feet of carpet to get there. I even had one move into a brackish tank once.

#8 Guest_gzeiger_*

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Posted 09 May 2011 - 09:41 AM

That's mildly terrifying.

#9 Guest_davidjh2_*

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Posted 09 May 2011 - 10:33 AM

They're the only crayfish I won't keep.

#10 Guest_nativeplanter_*

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Posted 09 May 2011 - 11:15 AM

Bleach kills everything, and volatilizes away without residue.


I suppose baking the substrate in the oven would work too. But not for those with spousal supervision - it's likely to have at least some sort of odor.

#11 Guest_dafrimpster_*

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Posted 09 May 2011 - 11:17 AM

I have some too. I am so shocked by the rate they reproduce I am afraid to sell or trade or give any away for fear they get released in the wild. My sunfish will eat the small ones. I thought about offering some here for shipping costs but I am even afraid of doing that. i hate to euthanize them. I tohugh about grinding them up as an ingredient in some homeade fish food... scary stuff these guys.

#12 Guest_schambers_*

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Posted 10 May 2011 - 06:42 PM

That's mildly terrifying.


Yes, it is. Exactly what we don't want loose in the wild.

#13 Guest_Irate Mormon_*

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Posted 10 May 2011 - 10:27 PM

Copper should kill 'em off, if that's what you're about.

#14 Guest_dafrimpster_*

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Posted 11 May 2011 - 09:05 PM

The other scary thing is that they are for sale on Aquabid constantly.



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