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Stocking a 40 Breeder


New Member
I've got two 40 breeder's that are currently starting their nitrogen cycle. I've got a pair of A. Cacatuoides and a trio of F1 A. Agassizii that will each move into a 40 in a month or so. Both tanks will be planted with plenty of hiding places as well as some small caves for breeding. I'm thinking about 2 males in each tank with 3-4 females each but I'm not entirely sure on the territory they'll need. I seem to recall seeing some information that indicated males defend something like a 12" circle with females needing like 5-6". Am I being too ambitious thinking I can reasonably house & breed that many or does it sound reasonable?


Well-Known Member
5 Year Member
Wiltshire UK
Hi all,
You may be all right with 2 males, it depends a lot on species and how aggressive the fish are. I've had 4 male cac's in a smaller tank, but they were probably siblings and raised together. I've never had any joy with 2 males, it has always ended up with one dominant male and a very stressed sub-dominant male. I keep very weedy tanks, with lots of cover, so it isn't a line of sight issue. For the harem breeding species (like you are going to keep), you can have one male and at least 7 females successfully. That would be my suggestion a male and a harem of 3 - 5 females (if you have 2 females you may get problems with dominance) in a harem it gives the females a break when they aren't ready to spawn, whereas a pair the female tend to end up constantly harassed.

cheers Darrel

Mike Wise

Staff member
5 Year Member
Denver, Colorado, U.S.A.
Darrel is right, it really depends on the species, individual temperament, and layout of the tank. I recommend having a 1'/30cm diameter territory for each female plus extra areas where the male can go to avoid brooding females. Males are not as aggressive as female. Females are very hard on each other. Without enough (and large enough) territories, the subdominant females are usually lost.


Active Member
5 Year Member
Clarkston, WA
I would not use 40 breeders for breeding purposes unless after the fry are independent you plan to remove the adults from the tank so the fry have the 40 gal breeder for grow out space without the need to remove them.
Few Apistogramma trios need more than a 20 long, 12 X 12 X 30 inches for a breeding tank and it is easier to remove a pair or trio from a 40 breeder than it is to remove the fry.
If you really want to establish a more permanent breeding and rearing colony tank a 6 feet long, 125 gallon tank is an appropriate sized tank for permanent colony breeding and fry grow out. That seems like a large tank but it really isn't. It allows keeping 3 or 4 trios and enough space for rearing the fry to young adults. You need to harvest the new young pairs and distribute them in order to sustain your production over a long time.

I use 40 gal breeders as one of my standard sized tanks. I also use a lot of 20 longs, a few 29H for pairs of Discus and my L260 colony and a 75 and 125 gal because I raise Discus and need the larger tanks to grow adult Discus but I breed all my Apistogramma in either 10 gal or 20 gal long tanks and use the 40's to rear the fry to a salable size. I am able to raise 25 juvenile Discus to 2-1/2 inches which is my salable size in 40 breeders or up to 50 Apistogramma depending on the species to young adult breeders.

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