Quote:
Originally Posted by Dmaaaaax
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Beaslbob's explaination is good but does not quite work as you think with some chemicals. Suppose the ppm is constantly going up faster than you can remove it. Lets start with that 100ppm scenario and lets say that by the end of each week it goes up 20ppm. If you do a 10% water change each week here is what you get:
Week 1: 90ppm
Week 2: 90+ 20= 110ppm (10%) = 99ppm
Week 3: 99+20= 119ppm (10%) = 107.1ppm
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FWIW the analysis I presented represents what the tank will be at once the value before each water change is the same.
In your example you are changing out 10% of the water each week with a 20ppm increase between water changes. Assuming 0 in replacement water and applying the above equation:
(build up)/(fraction change)=(20ppm)(10/100)=200ppm
Reagardless of what the initial values was (90, 50, 10, 500 300, 200ppm) the tank winds up at 200ppm which is why at 90 it is still increasing each week. the tank winds up at 200 then down to 180 after the water change and back up to 200 then next water change.
One my tanks setup with sand in 2002 I do have a build up of both kH an dgh to very high levels. On my 2 year old tank with peat moss kh has been 4-5 degrees an dgh 9-10 degrees for th eentire 2 years including initial setup. So the peat seems to be helping keep those constant and neon tetras seem to need that.
my .02
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fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks.
http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden