Convict - Can they be kept under control?

[elting44]

I don't think you can avoid it happening. If you catch all the fry and chuck them into the main tank I'm pretty sure some will survive especially if there's plants and wood and other hiding spots, before you know it a nice new pair to add to your collection!

^This

Every established pair of convicts I have owned will eventually spawn in a completely random spot even if they have laid in the same spot for the prior few spawns.

I had a large cave in the center of a 55g. My primary pair would spawn in the right section of it 75% of the time. The other 25% it was a roll of the dice. This went on for years

 

[Madou]

Pimelodus blochii are not as active as pictus in my experience.
Either way they would not be unsettling to convicts.
There are many astyanax species available not just the blind version of mexicana.
BA tetras look simular and would do the same job.

I like these much more, though I'm concerned about their small size.
Afraid the pikes would make quick work of them.

Unless I missunderstood, and you meant that I would add those into the 90 to keep convicts in check, right as they spawn rather than put them in the 180 to keep whatever fry I catch to feed and avoid them breeding.

I am so very sorry, I am a very picky person with very odd taste.

 

[elting44]

Also, In my experience, parents stop protecting the fry and will cannibalize the young once they are 1/4" to 3/8" or as soon as they being the spawning process anew, unless the fry are separated. In the aforementioned 55g with plenty of nooks and crannies for young cons to hide, usually only 2 or so would survive into juvenile/sub-adulthood. The rest were eaten by H. Multispinosa or other convicts.