It would be good to clarify debris since a food flake does not show up in TDS until it starts dissolving completely into ammonia, phosphate, etc. If you can lower your TDS using mechanical filtration, that only exposes that your previous filtration was inadequate.
I don't understand why this is the case, but tannins (or maybe related acids) from driftwood, leaves, and cones tend to increase TDS while peat moss actually absorbs many things causing TDS to decrease.
While TDS by itself is pretty useless, it is very helpful in a somewhat closed system where you are trying to gauge changes you are making (such as adding fertilizers or watching nitrates).
I care because it gives me a quick glance at where I was, where I am, and helps me know where I'm going (TDS increases as water evaporates and I add ferts, so if my TDS is dropping, I know I'm not adding enough ferts).
I just wanted to point out, that i observed my tds dropped down after i connected second filter, my tank is 20 gal long and in my case it was much better idea to use 2 filters on each side of the tank, and i dont use any food flakes or other messy pellets, it's only shrimp tank. Im my case high tds was caused by lot of debris from Driftwood and leaves, all params stay stable only tds is low
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