I found 3 unexpected babies in the tank!

Hi guys, I never posted on this forum and have no knowledge at all about bristlenoses. I have a Rio 300 ( a bit less then 300 liters of water) where I decided to grow few small altolamprologus calvus. I must admit this species is highly  recommended on fish forums but I am not satisfied with them . In any case the reason why I am writing is that in that tank I have two albino ancistrus. These are highly neglected because the water is hard and alkaline ( good for the calvus) and I have not fed them for a long time because the mopane rock in the tank is covered with algae. I find a massive amount of poop on the gravel. So I think they do eat.  The tank is filtered with two big canister filters. I also think they feed on the leftover food of the calvus which is not good for them being very meaty.
Well, yesterday I found a baby ancistrus. Then other 2. I did not know what to do. I thought to net them and put them into a small floating tank. But the feeding would have been a problem and in the tank they have much more opportunities. So I left them there and 24 hours later they travel along the glasses. The biggest is 12 mm long and the other two are around 10 mm. The parents are small fish, not more then 6 cm each. I never expected babies from them. I never studied the reproduction of the ancistrus and would appreciate to hear from you what happened.  What I believe is that the eggs hatched and most of the fry were eaten by the calvus and for some lucky chance these 3 survived. Is this correct? I base this on the fact I cannot think they hatch at 12 mm. The next question is can I keep more ancistrus in that tank? I read they are territorial but the tank is quite spacious. Any advice is welcome. Thank you.

Hi &   There is a good chance the babies were eaten by the calvus but also dad could still have them with him although at that size not likely.as for keeping more I would go for 1 more male and 2 females although others might not agree with me.

Thank you. I found the bigger baby killed by the calvus, so I netted the two which survived and put them into a floating tank. It is small but at least they are safe.

Yeah, Calvus are very strong predators and would be top of my list for reasons that there are not more fry.

Also, the hard water may have reduced the success of the breeding.

Keeping the babies in a smaller floating tank is a good move.

Thank you Doug. The two little ones in the floating tank look ok to me. I am thinking to put the parents and the babies into a is active but soon will be with no fish. Just to see if the can breed better. The babies I feed with boiled baby marrow. Can I give small pieces of Hikari algae wafer?

Yep, they will love a bit of algae wafer

Thank you Doug.