No idea
The Alparex worked again for me with trich (not costia this time had none
)......not cheap at £35 for my pond i thought......but on reflection it worked so it was 
. I,ve had failed treatments for flukes and moaned , pp failed for costia / trich at a dose i would not post up ( sturgeon removed ) .
Thinking about why over and over again has done my swede in ......Works for others so whats going on ?
The fluke treatments that have failed in my pond like "fluke solve" and " fluebenol based stuff " ......i,m pretty sure i,ve nailed the reason why and its not the products fault or use by dates .
I have probably done fluke solve and fluke m an injustice saying they failed ?.......they did on my pond but it could be user error or rather my set up .
So .....i,m guessing the reason is the same i could not get the costia for more than a few weeks last year with pp .
I,ve got one more test to do on the pond in a few weeks and flukes to kill on a goldfish from the pond with products that have failed in my pond .....the goldfish is in a tank for treatment ....
Its obvious on my pond and a pure guess why others have had failed with treatments that work for many others .
Anyway ....
Will run it by you ladies / gents in a few weeks to see what you think
Is it sad to get excited about a " light bulb moment " on fish meds
