Hmm. That's a tough one. So you currently have 3 swordtails in a 29 gallon? What are your water parameters? Perhaps the water quality is the reason they aren't making it... otherwise, I have no clue. I will promote your post if water quality is not the issue. Hopefully we can help you figure out what's going on.
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Phishie

"An ounce of prevention is worth a pound of cure."