it will be better for them as they are a shoaling fish, the more the merrier. but i wouldnt go more than 6 in a 2ft tank. be patient if they have spawned once im sure they will again, it may be a week a month 2 months etc etc. they will do it in their own timeI know it won't make them spawn but it will make them happier. I just thought with a larger group they would feel more secure with the guppies always mooching around the bottom and scaring them off.
Alessa x.