ok lets start with the basics for everyone else that doesn't already understand what a
wet/dry (or trickle) filter is
also, see podcast episode 46 for more info
Q&A #5 - Podcast Episode 46
This is a type of filter that contains a large open area that is filled with some type of media, either plastic bio-balls, small ceramic rings, or other ceramic materials in various other designs. while the designs vary the end result is the same. These filters aim to handle most of the biological filtration for your tank. water is they drained or trickled over this media keeping the media wet, but the media is never actually submerged.
so what does this do?
well this creates a very oxygen rich (or aerobic) area. and this is where the types of aerobic bacteria. this is the bacteria that processes the first few stages
ammonia ->
nitrite and then
nitrite ->
nitrate
this final stage has to be tackled by another bacteria that is found in low/no oxygen areas (anaerobic) this conversion is of
nitrate -> to nitrogen
but then you ask an important question, well if you only have X amount to raw materials how can you end up with excess of the final product.
in other words, how can you end up with a house with only 10 2x4's
That is a great question, and here is how...
so lets setup our example here with some very pretend numbers.
the details im going to use here are very inaccurate, but the results are the same, and relevant
So lets start with our tank running with not enough bio filtration, IE not enough
LR,
DSB, wet dry, etc...
we have our tank running, and it starts the day with 100 units of
ammonia. our inefficient bio filtration reduces this to
70
ammonia
10
nitrite
15
nitrate
5 nitrogen
(again these are pretend units for this example)
now we need need more filtration so we smack on our
wet/dry.
It being an insanely efficient device clears out the first parts as follows
0
ammonia
0
nitrite
70
nitrate
30 nitrogen
hmm.. well we need to handle that
nitrate.. lets stock up our
live rock and insert a mature
DSB (we will pretend we can snap these items into place as mature)
ok, now with our mature
DSB and
LR we are at the following
0
ammonia
0
nitrite
40
nitrate
60 nitrogen
Hmm.. still way too much
nitrate, why is that, we have the
DSB and
LR..
well lets take a look at the same system with out the
wet/dry
our parameters are something like this
10
ammonia
10
nitrite
10
nitrate
70 nitrogen
(again, these are pretend units)
now lets introduce another piece and state that a test kit can only detect levels higher than 10 units (anything 10 and under register as 0 on a test kit)
hmm.. interesting.. what do we have here...
well what's really happening here is that the
wet/dry filter is just overly efficient. It's removing everything, leaving more
nitrates than your system can process.. when in fact the system without the
wet/dry is able to establish a balance it levels that are
a.) low enough not to bother anything, and
b.) low enough not to even show on a test kit.
so now after all of that, where does all that excess raw material come from? well it was there all along..
does this mean
wet/drys can not be used? absolutely not, however unless you fully understand your system, understand how these types of filters work, and have a plan do deal with it, then stay away from then in a reef tank. In reality many people find it easier to let the system balance it self out as they will do if setup correctly.
i really hope this help, if not by all means lets keep this thread going.
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