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A filterless tank thought

I just thought of a way to setup a filterless tank without
worrying about whether there will be enough filtration
for the fish.

Many people (including me) add KNO3 to their tanks to
maintain a level of nitrate to make the tank phospate
limited (the PMDD approach). In theory, by being phospate
limited, these tanks have enough plants to uptake all the
available nitrogen in the water.  It means the bacterial
biofilters (canister, wet/dry etc) in these tanks are really
not doing anything useful but competing with the plants
for the more desirable forms of nitrogen (ammonia and nitrite).

This offers a practical way to set up a filterless tank.  First,
a tank is setup as usual and go through the nitrogen cycle.
Then if enough plant is in the tank, eventually nitrate will
reach a very low level and at this point KNO3 can be added
to make the tank phosphate limited.  At this point, the
aquarist will know the tank is ready so the biofilter can be

This procedure removes the guess work of determining
whether there is enough plant/light/CO2 to support a
filterless tank.

Thoughts and comments?

Louis Lin