How much Interceptor should i use in a 75G tank and 120lb of live rock and a 30g sump. I know 1 tablet will treat about 380g . So how much of the tablet should i us ?
Your actual water volume is probably like 55 gallon or less, plus your sump.
I would probably estimate you can use 20% of a pill per dose. You won't see the rb's fall off until about the 4-5th hour usually. Overdosing a little doesn't seem to have any negative impact from my experience. I probably overdosed a little more then a little though.
If it is for killing red bugs it is 25 mg per 10 gallons of actual tank water. Each tablet is 1 gram with 23 mg of Interceptor. Just take one tablet and grind it up to a fine powered and dissolve it in 500 ml of RO/DI water. Then take 12.5 ml of that water which is about equal to 25 mg / 10 gal. If we amuse you have 50 gals net water, then 12.5 ml x (50 /10) = 62.5 ml for 50 gal net water.