# [Wet Thumb Forum]-Kent's Blackwater Expert



## flagg (Nov 29, 2004)

A couple of years ago I kept a diff. setup in my 30 gal. It was basically plain gravel that I rarely, if ever vacuumed, with many large live plants. I was surprised at how well it did considering all I did was fertilize the substrate with tabs. Didn't add any ferts or nothing either. Recently (read: about 10 minutes ago) I realized that part of the reason for my success (I was thinning out plants CONSTANTLY!) was that, in addition to letting mulm accumulate, I was adding Kent's Blackwater Expert and I think that this provided the extra iron and other nutrients my plants needed. I very successfully grew swords, vals, dwarf sags, foxtail and chain swords. 

Well anyway, what I'm wondering is if anybody else has had any experiences with the stuff (or anything similar)?

-ricardo


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## Jane of Upton (Jul 28, 2005)

Hey Ricardo,

Did you have algae problems? With the fertilizer tablets in the gravel, I would think that the nutrients would have a direct path into the water column, becoming available to algae as well. Most fert tabs contain iron in trace amounts, don't they?

Perhaps the blackwater extract had a inhibitory effect on algae? 

Was the gravel large grain, or small grain?
-Jane


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## flagg (Nov 29, 2004)

That was the best part Jane! It had zero algae. I mean, in retrospect, it was a minor miracle! I didn't know what I was doing, really. All I knew was that I couldn't afford CO2 systems (and yeast is just WAY too much effort!) or expensive lights. What's especially interesting is that the Kent's stuff contains chleated iron which, if I remember D's book correcly, is easily used by algae when it's in the water column. 

I don't know if the tabs released nutrients into the water, but if they did, the plants must have asbsorbed them. You know, now that I think about it, I think part of the success was due to the many water sprites that grew on the surface (including that 3 footer...) as well as the large amounts of duckweed.... Man, that was a nice tank....

-ricardo


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## Dave P (Dec 13, 2005)

Ricardo,

I haven't used the Kent product; however, my latest aquarium utilizes a 1" pulverized topsoil underlayer that, within the first 24 hours of submersion, liberated enough DOC (tannins and other humic substances) to turn the water black. It was as if I had a 46-gallon cup of coffee sitting in my living room! Except for the floating plants, there was no visible plant growth.

After two months, and eight 75% water changes, the water is still the shade of weak iced tea. I've ceased the water changes, and am relying on activated carbon in my quick filter to steadily decrease the DOC. Plant growth has now picked up dramatically; even the Vals, which I had almost written off, have stormed back with a vengeance. I have yet to see algae in this aquarium.



> Perhaps the blackwater extract had a inhibitory effect on algae?


This would be my guess as well. In Diana's book, she states that many DOC compounds such as tannins, phenolics, etc., have allelopathic properties that inhibit the growth of algae. The Kent product and the leachate from my soil underlayer are likely loaded with these compounds.

I could be wrong, but I think it was an excess of such compounds during the first two weeks of my new aquarium that not only inhibited the algae but may have inhibited the plants as well. That, and the fact that the light from two 96 watt PC bulbs was almost non-existent after traveling through the first few inches of water (this, I'm sure, played a much larger role than allelopathy







).


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## dwalstad (Apr 14, 2006)

Have you all not heard that pondkeepers use barley straw to fight algae? Someone even did a credible scientific study showing that it helped.

Just toss in barley straw!


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## Dave P (Dec 13, 2005)

Wow! This is fascinating!

A little searching found an article right here on Aqua Botanic: http://www.aquabotanic.com/barleyarticle.html

Make sure you click on the link to the straw study PDF.

I also found this link to a PDF documenting findings here in the U.S.: http://www.btny.purdue.edu/Pubs/APM/APM-1-W.pdf

I'm intrigued by two of the side benefits: improved gill function in fish, and the culture of infusoria and freshwater zooplankton. I've known for years, that one can create a zooplankton culture using straw; but improved respiration in fish, that's a new one to me. Hmm... (thoughts of a small refugium containing a scaled-down barley straw culture which is connected to the main aquarium with only a trickle of water moving between the two). I've got to be careful though; neighbors might think I'm brewing something in my living room.









Thanks for sharing this with us, Diana!


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## dwalstad (Apr 14, 2006)

Hi Dave,

Great to have you on board! And also thanks for posting the two websites. I'm sure that Robert was pleased.

The algicide (probably multiple polyphenols and humic acids) have not yet been identified. 
Like allelopathy via phenols and polyphenols, this is another example of natural and serendipitous algae control.

Isn't nature (and chemistry) great!


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