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[APD] RE: DOC and why you should do water changes/treat your catbetter

Someone said:

>What's DOC

Well there's two meanings.
Dissolved Organic Carbon.
Damn Onerous Cat

It's something few ever test for and builds up to a certain point in tanks
that do not get water changes.

I had a rough time testing the cat. "Hisses per day" is not a bad measure

By doing water changes frequently, you remove any plant, bacteria, algae,
fungi fish based organics that may/or may not interfere with
plants/fish/uptake etc.
If you want to remove unknowns, frequent large water changes works well to
keep things on the inorganic side.

Since you cannot possibly test for each type practically, I just do water
changes, it works.
Water changes can provide an easy method of estimating the dosing/ppm
levels, removes any unknowns/organic components, adds a nice jolt of CO2,
make fish and plants happy, algae seem to dislike it generally. 

The cat seems to like fresh chicken livers, doesn't hiss then.
Adds fertilizers a few hours later to the kitty litter substrate if you
have a trained "dosing cat"(very coveted).

Many of the organic compounds bind PO4, N, Fe and other trace metals making
them un/less available to the plants.
This is fine in slow growth tanks like a Diana Walstad non CO2 method tank. 

But if you want a good supply of available nutrients for a CO2 enriched
tank, then it's better to have the nutrients unbound and all inorganic
except for NH4.  
Many/most of the test kits also measure Total Fe, PO4 etc, not bio
available Fe, PO4 etc.
So if you don't do water changes, and you measure 0.2ppm of PO4 then you
likely have no ppm of PO4 available for the plants, it's all bound up in
organic molecules.

Now a cat can be tough to measure it's true onerousness. If it has a
hairball, it will not act right and be more onerous that normal. 

This is one reason why I suggest higher than some of the normal amounts of
fert's or mention about not letting things run too long for long. Many
times you will note that folks have a residual PO4 level of  0.2ppm.
Sometimes this is a bad kit, sometimes it's residual bound organic PO4.

This PO4 does get used, but....it gets used __slowly__. Bacteria in most
cases cleaves the bonds making the nutrients available to algae, plants,
other bacteria etc.
Carbon can be used, but water changes will do a better job IMO and also
have several other benefits.

Carbon is good in cases where you do not want to change the water for some
reason, salt water etc.

Tom Barr   

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