Tannin season in Panama

[duanes]

The rainy season has begun in earnest here, with almost continuous rain for the last week straight.
Because my tank is on the patio and surrounded by terrestrial foliage tannins flow off the plants and into the tank and especially the the 2 sumps carrying the tannins with it.
At this point I can't see to the back. Thought I'd take a couple quick shots before I dilute them with a large water change.

 

[duanes]

The rain leaching tannins onto the sump.

can sort of see the tannins, coming from the manifold that spreads out flow across that tank surface

 

[Hendre]

Pretty cool! Reminds me of the water in the mountains where I live, the fynbos releases lots of tannins (redbush tea is a fynbos species I think) which gives orange water year round in the streams. Do you just allow the leaves to break down?

 

[FJB]

That's a lot of tannins. Cool stuff!

 

[duanes]

During the dry season (maybe 6 months without real rain)the leaves and wood dry out and tannins seem to build up within, with the first heavy rains, its more drip-age from the plants behind, and above the tank, and some drainage off the roof into the sump, although some leaf litter falls in, it isn't a lot.

.

 

[duanes]

An interesting adjunct, is that one might expect with this plethora of tannins in the tank, is that pH would automatically drop.
Normal pH most of the year is around 8.
I did a low and high test a little while ago, and here are the results.

The tube on the left contain a low pH reagent (5-7ish), on the right, 7 to almost 9 reagent.

 

[duanes]

I was also curious to see if all that residue would raise ammonia or nitrate levels in the tank.

Ammonia still 0, but nitrate is slightly elevated.
The tank usually runs 0-5ppm nitrate, although hard to tell with the tannin staining I'm guessing nitrate is more around the 10 ppm+/- range,

 

[neutrino]

Interesting. How do your fish react to it?

 

[duanes]

The ones I can see seem fine, no glancing, or odd movements,.....this also happened last year, and they all came thru OK.
They all are ravenous when I feed (usually every other day, and/or whatever falls in the tank naturally) , about the only time they emerge from the tea colored water, and thickly planted background.
I have a feeling (no evidence of course) that the anti bacterial action of the tannins gives a kind of annual bacterial purge.

 

[neutrino]

I'd like the thought that due to how it's situated the tank mimics a natural cycle.

I'd have to search for it again, but I read a study at one point regarding fish's response to pH changes from natural causes, including significant pH drops after heavy rains, studying what they can handle without evidence of stress, etc. In the (riverine) habitats they studied, fish were far more resilient to pH changes, including relatively quick changes after a storm, than some hobby lore would have us believe-- not to say they're impervious, one object of the study was to note the limits at which they did show stress, even in their native environment.

Personally, as I've kept fish in varying conditions over the years (for varying reasons) I've noted what appears to be evidence that keeping some species near enough to their probable limit of pH tolerance (not meaning at their limit) may shorten their lifespan somewhat, despite being healthy, active, producing healthy fry, etc. all the while. I wouldn't call it scientific, just observation over the years, but my hypothesis is there's a long term range of conditions within which a species can live long, comfortable lives, a wider range within which they can live healthy but somewhat shorter lives, then outside this range where they're increasingly prone to stress or illness.

...Over the years I've adjusted accordingly to such observations, sometimes loosening up, sometimes tightening up-- depending on which phase of fishkeeping I'd been in at the time.

A field example I know of, though more about temperature than pH, would be S. haraldi discus, Bleher has documented finding them in water in the lower 70s (seasonal), but also said they looked less robust at the lower end of such temperatures.