Could you test the water parameters from the tank where you get the neons from? I bought cardinals a long time ago from one LFS, which were cheaper, but the water parameters were different from mine. None of the ones I bought from there survived. I bought more expensive cardinals from another LFS, but they use tap water for them, which happened to be the same as mine. All of which survived.
How do you acclimate them?
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125 gal (473 liter): Low Tech (1.5wpg PC for 10 hours, no CO2/ferts, gravel substrate), Equipment (72" Coralife PC, Eheim Pro II 2128 w/built in heater, FilStar XP3 w/Hydor ETH201 inline heater), Fish (6*Discus, 2*Angel, 5*Clown loaches, 4*L-018 Gold Nugget pleco, 1*L-260 Queen Arabesque pleco, 7*Cories, Farlowella cat)
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