Hey I'm not trying to insinuate you don't know what you're doing, more just verifying you actually measured it and weren't relying on dimensions given to you. I haven't attempted breeding firemouths, I only have the one but based on their low cost and availability I don't thinks it difficult. Buenos Aires tetras also make great dithers, i think you could add a group of six once you get your barb numbers up, that's at the limit though.
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