Hydrogen Peroxide 6% 1 Litre

Use 10 ml of 6% H2O2 per 20 litres of water for algae growth control.  Safe, at this rate to use with plants in place.

Use 2 ml per litre for system fungal spore cleaning.  Remove plants before adding this strength of Hydrogen Peroxide.

Hydrogen Peroxide has one more Oxygen atom than a water molecule and when this comes in contact with a living cell, it converts into water and oxygen.  The free  oxygen atom then damages the cell walls of bacteria and fungal spores . This is called Oxidation because the compound's oxygen atoms steal electrons from the bacteria's cell walls damaging them or even breaking them completely apart.

While Hydrogen Peroxide isn't always effective as an anti-bacterial agent, it is an effective bacteriostatic agent which means it can inhibit the reproduction of bacteria.  In doing so, it can help to avert the worsening of infections without actually killing all of the bacteria. 

It can also kill fungal spores (so it's called a sporicide) which helps to prevent fungal infections ( like root rot etc.)

For these reasons it is also used to disinfect surfaces such as cutting boards , counter tops etc.