You know, mine dont seem to play by the "bottom only" rule. The pygmies, especially hastatus corydoras, are known more for their midwater swimming than their larger counterparts...
But i see my aeneus all over the tank. They explore the plants, the bottom, the floating plants up top. Mine dont seem to follow rules lol. Mind you, i do notice of my species i keep some are more likely to be all over than others.
Paleatus (peppered) do like to explore taller plants and will play in the current a bit.
My trilineatus (false julii, three lined, etc) are mostly bottom lovers.
My aeneus (bronze, green, etc.), nothing applies, theyre everywhere. I have a few who will even come up to nibble my hands and fingers.
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Especially when they were little babies!
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But all over. They chase each other around mid water a lot too.
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My ambiacus and leucomelas are bottom most. Weitzmani maaaybe lower plants, but mostly bottom too.
I barely see my pygmaeus except at night. Very timid. But they sometimes come up and chill on the taller driftwood.
What is already in your 29? Its possible you may be able to have both