I was taught to make up syrup feed with fumidil in the following way. Make the
syrup by dissolving sugar in water as usual, and leave the syrup to settle in
the buckets, so that the solution is still. Then add the dose of fumidil by
sprinkling the powder on the surface, but do not stir. (If you stir at this
stage, the grains will coagulate, and will not be taken with the feed.) Leave
for 15 to 30 minutes. Each grain will absorb moisture. Then the bucketful can
be stirred and the grains will be evenly distributed, and will be taken by the
bees. Whether this is a true solution of fumidil in water, or a suspension, I
never took the time to find out. The advantage however is that it works with
cold syrup, so you are least likely to damage the antibiotic.
Regards
Matthew J Allan