Let's take 2.5% glutaraldehyde, for a real world example. It seems the most widely available product, and we can scale other strengths if necessary.

2.5% per liter = 2500mg per 1000ml (1 liter)

= 250mg per 100ml

= 25 mg per 10ml

= 2.5mg per ml

10 US Gallons = 37.85 liters.

If were were to add 1ml of the 2.5% solution to a 37.85 liter tank (10 US Gallon) tank, we would have 0.066mg per liter or 0.066ppm concentration in our aquarium. Since the MSDS on glutaraldehyde states that toxic effects can be noted, with very sensitive species, at .1ppm on up (and yes, we can see that, at the amount we use in our aquariums, it kills the algae, doesn't it?)

So, if we were to add 2ml of 2.5% glutaraldehyde to a 37.85 liter aquarium, we would have have 1.32ppm (1.32mg per liter) -- 1.5ml of this 2.5% glutaraldehyde to 37.85 liters would give us .099ppm, or just a hair below any observed harm to biological organisms (should not even show any harm to algae.)

I would think a 2ml per 10g first addition, with 1.5ml additions every day, or every other day would be fine (and, I suspect that the higher 1.32mg/ppm is even below the recommended dosage of Flourish Excel--but DON'T take MY GUESS as any sort of proof!

jmhart, being a chemist, please check and double check my figures, let's correct any errors I have made--others are welcomed to do the same also ... thanks in advance.

Regards,

JS