Dissolve the 5 grams of medication in a known amount of water. An 8 ounce bottle of drinking water would be good. You know there is 8 ounces there. Now, half of that, 4 ounces, will treat 50 gallons of water. 2 ounces will treat 25 gallons. When you have done your treatment, mark the bottle with a permanent marker as to what is in it, cap it tight and put it in the refrigerator. It will keep for 3 months there but I would throw it out after 2. You might tape the cap closed just to keep others from trying to drink it. It is not really harmful but not intended for human consumption. It taste terrible! Very bitter and tends to cling to the palette."
I think, if I had a ten-gallon tank, I would dissolve half an ounce of the medication in that 8 oz bottle and administer it to the tank. Hope I scaled the math correctly. ;)

Yes you could probably freeze those accessories. You could leave them in the sun and weather too. Actually you could leave them in an aquarium with nothing else in it (no fish, snails or small critters) and the larvae would starve in a day.

Maybe I'm making treating too difficult. Just trying to point out that we do spread diseases through our equipment, if we are not careful. :)