Hello! I think you raised an interesting question. Let me just share my thoughts on "profit" resulted from breeding fish. Technically, in order to find out your profit you need find out your break even quantity first, which is an quantity you need to sell without making or losing any money. But lets make it simple. I live in USA, a piece of C. sterbai runs about 4-12 dollars in my LFSs. Online, on aquabid.com, currently I have seen someone sold it for less than $3 a piece. The time takes me to grow my fry to a sell-able size usually 3-4 months. Fry food about $20-50 for 100 fry. (well, this amount will drop per fry if I can rise a larger quantity.) Now, lets account other costs that usually people ignored. Utilities: water (including water conditioner, RO system if you use), electricity per month guesstimate about $20-30. Fry cost: not every fry that are sell-able, some are just genetically weaker than others. My breeders are F0, so no inbred problem IMO. But I still have about 5-10% problem fry that can't sell ( or at least I don't sell) which really means you are adding more costs. Of course, last thing, your fish may take a break from breeding (at least mines do) and the lead time should also be considered. After you have accounted all those (keep in mind, we have NOT account any initial investment yet, ie, tank, heater, filter, light, etc) your break even quantity is fairly high. This really implies you need to bred large quantity in order to recover your costs. Another point, you mentioned dwarf cory. I personally haven't breed those guys yet, but a good friend of mine breeds pgmy cory. He told me they are not so prolific, so this could raise another problem for you to recover your money, worse thing is those cory are considerably cheap in my area, about $2 a piece. In summary, if you treat this as a business and properly account all relevant costs and still want to make money, quantity really makes a big difference assuming your don't compromise quality. On the other hand, if you just want to breed and raise the fry for fun, nothing should be consider (ie, all variable cost and selling price) because it is simply not a business.