FishNoob wrote:
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Its main ingredient is tea-tree oil, right? I know that has great
antibacterial and anti-fungal properties in other situations - why is
it less helpful in aquaria? And what would you recommend instead?

Sick mollies are easy to heal. Salt 'em. Mollies can even live in
seawater. Put them in a quarantine tank or even a pail with an airstone
and gradually add salt over 48 hours until it's 6 grams/litre (2 US
tbsp/gallon). This will kill all freshwater parasites and most
bacteria. Keep ammonia down with AmQuel and frequent water changes
using salted water. Once the mollies are well, very slowly lower the
salt with water changes until they're back in fresh water - plan on it
taking at least a week. (Do NOT try this with anything other than
brackish water fish.)

My take on Melafix: Tea tree oil is not water soluble. In human
medicine it's used anywhere from 1% to full strength in an oil or lotion
base. You're nowhere near that concentration in a fish tank. Besides,
have you ever smelled fresh tea tree oil? It's got a very
characteristic scent and Melafix isn't even close. Any real or imagined
effects from Melafix are more likely from all the solubilizing agents
(ever notice all the bubbles from it?) than tiny amounts of tea tree oil.

Is it mostly your mollies getting sick? Your water may be too soft for
them. Mollies seem to like either hard or slightly salty water. Plants
will tolerate 1 tsp/5 gallons of salt (0.02%) and sometimes even that
much helps mollies stay well.

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