Organics in water column

seangee

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Just curious but there may be a question in here somewhere.
All my tanks are under-filtered (according to filter manufacturers of course) and the only filter media I use is fairly coarse sponge. The water always looks pristine and nitrate always stays below 5ppm. I also do a 75% change every week.

Yesterday I added some sand to my 200l community tank (may be a clue there). It has an HOB with sponge and the flow turned down to minimum. I also have a low powered pump that I use to circulate water and the inlet of this is attached to a double sponge filter. I rinse these sponges weekly and they turn the bucket suitably mucky :).

To get the new sand into the tank I scooped out all the frogbit and stored it in a bucket while I worked. I also netted out as much of the duckweed as possible. Job done, frogbit back and I decided it was time to up my game in the duckweed battle. So I found an old tiny pump and made a mini surface skimmer. The collector was only small as I used the bottom of an old gravel vac for this, naturally I put a wad of filter floss in so the the duckweed did not get sucked straight through the pump and back into the tank. The skimmer was surpisingly effective in that it is powerful enough to catch and hold duckweed, but not powerful enough to trouble the frogbit or fish. So its going to stay for a while because catching a couple of tablespoons of duckweed every day with zero effort has to be a good thing. But I digress...

Within a couple of hours the filter floss was pitch black. There are tannins in the water but I was surpised at how much the floss had collected. It was 6 days since the last water change. I immediately did a nitrate test (twice) and it was almost zero (almost pure yellow on the API test). For good measure I waved a strip at it and that showed no detectable nitrate. I collected the duckweed changed the floss and left it running for another 24 hours. Interestingly this time the floss barely changed colour in 24 hours - suggesting that in 2 hours it had cleared most of the organics.

So (finally there is a question after all) should I
  1. Add a bit of floss to the filter(s) and replace weekly
  2. Run my home made water polisher in each tank for a couple of hours a week
  3. Let it be. Fish and plants are healthy, tanks all look good and organics in small amounts are an expected and neccessary by product of a living eco system.
 

Byron

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I would wonder if the filter floss was not actually filtering out microscopic suspended particulate matter from the sand?
 
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seangee

seangee

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I wondered about that which is why I mentioned it. TBH the tank doesn't look any different. No point in checking the other tanks now because their w/cs have just been done. I'll leave it to collect duckweed for a week and try one of the other tanks just before the next change.
 
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