Planted Tank Guru
Join Date: Apr 2011
Location: Hamilton, Ontario, Canada
Population density and breeding
So after seeing many threads about not breeding and people expecting 10 shrimp in a 20 or 40 gal tank into hundreds, I thought I would start a thread to get people opinions and maybe something for people to find when reading when it comes to breeding.
This is my understanding, and feel free to correct me if I'm wrong.
A female develops unfertilized eggs in her back, which we refer to as the saddle. When the time is right to her; temp, water, minerals, phase of the moon, day of the week, whatever factors they use to determine, she then molts, and two things happen. She releases pheromones in the water which attract the males, and her shell becomes soft. If a male copulates and leaves his sperm, she passes the eggs through her body and the sperm and they become fertilized and she then store them in her lower plepods to carry to term.
The window in which a male can fertilize her, and this the eggs is only a few hours until her new shell starts to harden and that process can't happen again until she molts again.
This leads me to my theory, that if you are starting with a small population, start them in a small tank. I myself tried to thin out my population and try breeding in different tanks and got dismal results. Trying to put my CBS and CRS and goldens all in different tanks and then by grades, etc but when you only have a few of each in a 10 or 20 gallon, it's a rare chance the male can make that window or even find her. This is leaving out fertility problems of the male or female, which I'm sure exist as they do in every creature on earth.
Heavily planted tanks affect this as well. Lots of places for the female to not be found during that window.
When I culled all my cherry shrimp and PFR's that I mixed together as a noob, I had a few nice females in a tank with a few males I wanted to keep. It was a 20 long. No breeding. Put them in a 2.5gal and blame, back to back to back to back berries. Plucked out babies and culled as fire reds or cherries and now I have a very nice solid red population of at least 200 shrimp at any given time and sold hundreds from the tank, where as keeping 5 shrimp in the 20 long, I doubt I would have been anywhere near there.
There is nothing wrong with having a nicely planted and scaped tank, but if it's full and lush and you don't size your population according to the tank size and coverage, I don't think you'll get the breeding you expect. My best results now are a population sized to the tank, and bare tanks. Setup a small tank with some moss if you only have a few shrimp and get them breeding in it and pull babies out to populate your "show" tank.
I think you'll get much better results. If you are a male or female looking to randomly "hook up" with someone, are your odds better in the middle of a campground in a forest with 4 random campers spread out over 10 miles or in downtown New York at rush hours randomly asking people?
20g platy, , 2 x 10g shrimp, 3 x 20g shrimp, 7.5g shrimp and 1 great dane/mastiff puppy.
Sump Pimp #2
My Tanks and my shrimps