Richard bray

Biological Surface Area
Biological surface area (BSA) is any surface area within your system, athough the most important are your grow beds and biological liters. The more surface area, the more bacteria can colonize your system. As bacteria grow and reproduce, they become more effective at nitrifying the ammonia.
This is why media-filled beds are able to support plants with heavy nitrogen needs. The grow media provides a lot of surface area for bacteria, which transforms large amounts of waste into nitrogen. It
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also helps support a higher stocking density in your fish tank, because it can filter out waste at a higher rate than a DWC system.
This is also why many media-bed growers prefer clay pebbles over other media options. Porous grow media adds even more surface area for bacteria, which helps filter the water better, and feeds plants the maximum amount of nitrogen.
However, a biological filter can achieve the same results as a media bed, which is why you must add one into a DWC system. These filters add a large amount of surface area, just like a media bed, where bacteria can colonize and nitrify ammonia.
BSA is calculated by finding the square footage per cubic foot. Porous grow media, like clay pebbles, have a large amount of surface area, but they take up very little space. Once you choose your grow media or biofilter media, calculate the volume it will occupy, and research the square footage per cubic foot for your media
Media y2" Gravel 1" Rock 1" Plastic Bio Balls 2" Plastic
Bio Balls
Sq' per Cu’ 85sq' 21sq’ 85sq’ 48sq'
For example, if you have a grow bed that is 4’ x 8’ x 14”, and you want to fill it 12" deep, then you will have 32 cubic feet of grow bed space. Ill you use 1" rock as your media, you can calculate your BSA by multiplying the square footage area of 1" rock (21sq') by the amount of cubic feet in your grow bed (32’).
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The math will look something like this:
4' x 8' x 1’ = 32cu'
21x32 = 672sq’ of surface area in 32cu’ of grow bed space.
With a low stocking density of lib of fish per 10 gallons of tank water, you need at least 25sq' of BSA per pound of fish.
So, if you have 672sq' of BSA in your grow media (not including the surface area of your grow bed) then you could support at least 26 lbs :f fish with your grow bed. If you want a higher stocking density, you may need as much as 50sq’ of BSA per pound of fish.
pH
The pH values of your system have a substantial effect on the nitrification process. Nitrification will result in a lower pH value, but if a pH value is too low, nitrification will slow down or halt. Consequently, the pH may begin to rise, but not before your plants and fish suffer.
If pH adjustments are made gradually, the bacteria can usually acclimate and nitrification will proceed as usual. However, large doses of pH modifiers can kill off the bacteria that enable nitrification, which can cause a system crash.
A pH between 6.2 and 6.8 seems to be ideal for nitrifying bacteria, although they will still function at neutral. If you need to adjust the pH of your system, do so gradually and before the pH dips below 6, in order to preserve the health of your bacteria.
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