I hope I can give you a little guidance here, being that I have a heavily planted tank, and have had reefs in the past.
A quick rundown on the major chemisty differences between a SW
reef and a planted FW
tank, aside from the salinity:
In the FW
planted tank, NO3
becomes a natural fertilizer. It is the waste byproduct of the completed breakdown of ammonia in the nitrogen cycle.
----> consumed by nitrogenizing bacteria A which produces ------> NO2
as waste, consumbed by nitrogenizing bacteria B which producee ------> NO3
. end waste product.
is then consumed by plants, as a fertilizer.
The level of NO3
in a FW
tank is cosiderably higher as an acceptable level in a SW
tank, as the SW
species have a much, much lower tolerance for NO3
poisoning, and there are no plants to fertilize (except algaes, in which case macro algaes can help keep the level of NO3
down in SW
The nitrogenizing bacterias in FW
will live on any surface they can attach to. Because FW
fish are often accompanied by plants that can utilize the NO3
, and are more tolerant to NO3
levels, often, water changes can keep them acceptable, and further breakdown of NO3
is not needed.
However, the SW
side is a bit different.
keeping, live rock provides ENORMOUS anaerobic surface area for a possible third bacteria to live, nitrogenizing bacteria C for the purpose of this discussion. Bacteria C is an anaerobic organism, requiring a lack of oxygen to thrive. It will take the NO3
waste product and further break it down to N- gas, which is then released in the water column.
Much of that is, however, theory. Most SW
keepers avoid high levels of nitrogen byproducts and ammonia via protien skimming, which removes large and minute waste particles from the water column via frationization before they even break down into ammonia. Also, due to the increased presence of proteins in SW
tanks, live rock surfaces provide large amounts of surface to break down these nitrogens.
Bioballs, in the SW
tank, do not provide the same porous surface in SW
as they do in FW
. Likewise, the bacters that work the nitro cycle in SW
are not the same as FW
. They often work better directly in the water column. Bioballs tend to work almost "too well", creating a NO3
"nitrate factory" which spills into the water column, and increases the levels in the tank. A FW
tank and it's inhabitants can handle levels of NO3
upwards of 50ppm, while SW
inhabitants, especially inverts/corals cannot tolerate more than 10, preferrably less than 5 ppm
Therefore, many SW
keepers introduce LR
rubble to replace the bioballs to avoid the "nitrate factory". Also, SW
husbandry habits tend to differ from FW
husbandry in that 1.) corals and inverts are in abundance and are animal lifeforms, not plants, with increased value $wise, and higher sensitivity to poisoning (see articles about the difference between animal cellular structure and plant cellular structure), and 2.) often, SW
keepers do many more smaller water changes than FW
keepers. Usually in the neighborhood of 10-20% 2-3x weekly, to further assist in reducing NO3
. and 3.) plants can and do utilizes NO3
as fertilizer and food, and having a consistantly increased level of NO3
is actually beneficial to their wellbeing, while in SW
tanks, there is nothing to utilize the NO3
end waste product.
hope this helps explain some of what you are asking.