JKUK

Hi everyone,

Does anyone have any experience regarding what happens to the visible tannin levels over the long term, if water changes are not carried out?

The reason I ask is that my first El Natural tanks are now coming up for six months of age. The water quality is so good I see no real reason to do any water changes yet. The level of tannin (yellowing of the water) however seems to still be increasing. While I personally don't mind this look, if it continues to darken it will eventually spoil the look of things. The fish are enjoying it.

Is the tannin level likely to stabilize or even decrease over the very long term?

Many thanks

dwalstad

Tannins could decrease, depending on the tank environment:

• strong lighting would photo-oxidize the tannins
• aeration would encourage faster bacterial decomposition (most tannins resist bacterial decomposition, which is why they accumulate)
• decomposition of soil organic matter and the resulting tannin production slow enough that tannins get destroyed faster than they accumulate (this is why well-established NPTs don't accumulate tannins)

For your tanks (no water changes for 6 months and tannins accumulating), I recommend water changes and/or adding charcoal to the filters. At some point, the tannins may absorb so much light that they inhibit plant growth.

Mr Fishies

When I first set up my tank, the soil I used leached a lot of tannins and the water turned yellow until after 1-2 years most of the tannins had been leached out. Now the water seems to stay quite clear for the 2-3 months between water changes/trims.

It's not harmful as you already know but you do loose some lighting efficacy in terms of what is absorbed/blocked by the tannins and not reaching plants. For your "reading pleasure", a few years back an old member did a bit of an experiment was done to measure the effect of water changes vs. light penetration.

dwalstad

Thank you, Ian. I was thinking of this experiment when I wrote my post, but didn't know where to find it!

JKUK

Thanks for the info as always,

For the moment I think I'll just do some small water changes, as my tanks are now mainly planted with Crypts ,and I don't want to give them an excuse to melt.

I'm not a big fan of using carbon in this type of tank .........things are beautifully balanced right now so I wouldn't wish to upset the chemical balance.

Thanks again.

cah925

I had some wood release tannins and after a while it actually stained the glass. I was able to clean it off easily, but I had to tear the whole tank down to do it.

The next time I did this, I used Purigen. I had to change the bag about 2x weekly for about a month, but the water stayed clear.

jazzlvr123

you can also just do frequent water changes like once or twice a week for the first couple months this usually flushes out your tank of any leeching tannins from wood aquasoil etc. that are usually expelled in the first couple months of setup. after about 2-3 months you'll hardly notice any discoloration of your water unless you don't do a water change for a month or so. keep in mind there is no safe way to rid tannins out of your water for good. there is always long term leeching but it is a much much slower and can be easily avoided by a simple water change but until things settle out I would say frequent water changes is the healthiest and best way to rid your tank of excessive leeching until things settle out.