DenMac, I trust you did get a positive coccidia diagnosis on the fecal sample?
Here are the instructions on mixing the Corid with water:
Water Tank Mixing - Treatment | Prevention and Treatment of Coccidiosis
Get a 20-gal water tub at the feed store.
Get some strawberry Kool-Aid (at least 10 of the small envelopes).
Put the appropriate amount of Corid for treatment in 20-gal of water and add one envelope of the Kool-Aid.
The Kool-Aid encourages the animal to drink the mixture. (This is vet's advice, and it works).
Make sure that you check the level at least twice a day so that the animal doesn't run out of water if it's hot.
After 5 days of treatment, you should see results (no more wet gloppy manure on the calf's rear and tail).
Then you will switch to using half the Corid for 21 days, mixing it the same way, with the Kool-Aid.
Yes, it's a month's worth of work, but it works. Using a smaller (20-gal tub) ensures that the Corid is replenished regularly.