Atm I have a 37 with a male and female and 10 guppy fry.
I'm leaning more and more into making that tank a BN breeding tank, but I was wondering how many BN I could keep in it. It has a filter made for a 75, driftwood, live plants and gravel bottom.
With sufficient water changes could 6 live happily in there(2 males, 4 females) or would it be better to just have 4(2 males, 2 females)?
The only thing that worries me is males fighting, there are plenty of hiding spots and caves so I don't THINK that would be to big of an issue, but I'm asking just to to be sure.

Beaver

I'm assuming that it's 37 litres, if I'm correct then one pair/trio would have to be the option, a good rule of thumb is 1.5 sq ft per male, but even then the fry would soon have to be moved to a grow on tank.

Males can be very territorial when mature and although there may be plenty of hiding places a 37 litre would be to small for two males to breed in.

Ideally for Bn's the filter would need to filter 200 to 300 lires per hour.

Oh, sorry I didn't specify, its 37 US gallons, and the filter is rated for 75 US gallons.

So that makes it 140.6 liter tank and the filter is for a 285 liter tank, I'm not sure how many liters/gallons per hour that is though.

Going by what you say I would have to go with a trio for that size tank. Guessing it's a 3ft? I have 2 trios in a 4ft 55G and there's no fighting but my big male is the boss. When my smaller male was on eggs the big male kept stealing his cave so I'm going to put a divider in there. Some people say 1ft territory per male but I like to play it safe with 2ft

Now that i'm thinking it over, 3 or 4 plec's(only one male) does seem better than 6, more room for the fry.

Careful not to overwork your male tho

true that. I'm thinking of switching my male common with my male calico every few months to keep either one from getting tired out.
Would that stress them out too much?

nope, as long as you introduce them into the tank properly. if they are in slightly different water then you will have to aclimatise them properly. if the water is identical then i just throw them around

Oh ok cool, cause I have two males in two different tanks and my parents have a 72 gallon rainbow tank, and I saw a beautiful albino short finned male at my LFS, and we are going back there today, so he could live in the 72 till I decided to switch him into the 'breeding tank'...if my mom lets me get him, i'm broke right now. But my mom has let me set up a 110 gallon land hermit crab exhibit for my b-day last year, yea, shes pretty awesome.
Either way, headed to the LFS today to see what they have. Might end up getting some off aquabid or some other online source cause I really want some L144 and i've never seen those here. I like super red's, but if I was gonna get those, i'd want to breed just super reds, and not cross them, and I don't have a tank for that.