Duck weed or no duck weed

Traditionally, we were all taught to hate duck weed. It did not belong in the aquarium, supposedly. Recently Matt Owens' book, The Alternative Aquarium: A Robust Habitat changed my mind, and since then I've been studying a Dutch site on ecological aquarium keeping as well. And the more you start researching Duck weed online it gets positively interesting.

Duck weed hoovers up ammonia, nitrites and nitrates, and it oxygenates the water - and then to think people did not use to like this plant. There are many interesting posts and articles to be found:

• http://www.guppies.com/forums/showthread.php/18686-Duckweed-and-waterquality-a-blessing-in-disguise
• http://www.planetcatfish.com/forum/viewtopic.php?t=26791
• http://www.mobot.org/jwcross/duckweed/duckweed.htm

It makes me wonder, how did I ever get by without it? The general principle seems to be that plants under water do not get but so much CO2, whereas plants that grow out of the water, or in this case, that float on top of the water, can absorb CO2 from the air, and therefore can grow much faster, and in the process absorb the fish wastes, which are nutrients to them.

Besides all of the wonders of sucking up nutrients at a fast rate, there is also the fact that it slows down evaporation, and therefore it is an alternative to a canopy, if you want to have an open tank...

As my new 29 gallon tank matured, and ammonia and nitrite finally went to zero, initially my nitrates were as high as 40 ppm, or even higher, upto 80 ppm at times, but duckweed was well... growing like a weed, and while I recently did a partial water change, I also just harvested some duckweed to see if it will indeed end up lowering the nitrate level, for my tank is fairly thinly populated, with just 5 amano shrimp (I think - though I started with 6...), and 5 pygmy cories. In the end however, with Duck weed (and Hornwort, and other plants), my nitrate reading is typically in the 5-10 PPM range, without water changes.

Here are some recent pictures:

4/28, with Duck Weed cover...

5/4 with the hidden LED to penetrate the cover

and some of the occupants:

5/4 pregnant Amano shrimp walking out of the picture

Ok, so I gave up trying to catch one of them in the picture, but there are three pregnant females... of the original three males I recently can find only two, so maybe one gave up the ghost during my two month tank cycling period, which seemed to go very slow at times.

Be that as it may, they do seem to be thriving, and my five Pygmy Cories, who don't pose well for pictures either, seem to be doing very well also.

The biggest challenge with the Duck Weed has been the lighting, for it not only slows evaporation, it also shields the light.

Duck weed and lighting

I was getting concerned with the weakness of the light, and it seemed evident to me that the plants needed more. 

The lighting has evolved to:

• Hagen Flora Glo, which has the right color temperature for plant growth (2,700K). but low output (650 lumen/90 LUX). At some point, I may consider replacing this with a Life Glo Bulb, which has higher output (1,470 lumen, at 6,700K).
• A Deep Blue Micro 3W LED SolarFlare, which gives the Wisteria some needed light. Color temperature is 6,700K daylight. 
• A Marineland 21"Hidden LED that clamps to the tank frame inside the lid, and penetrates better through the duck weed, being right above the water line. It has 72 LEDs, with Par/Lux at 12" 25/1121 and at 24" 11/377, with 550 lumens, and the color temperature is 6,500K, which is daylight.

This is still not high intensity lighting you would need for serious plant growth, but with fairly regular, low light plants, it will definitely do. All in all it is a modest, but workable solution. The Wisteria is growing by leaps and bounds, and soon I'll be donating plants to the pet store... Two Amazon Swords produced three offshoots, which are catching on. The problem area is the excess shade below the massive Wisteria, so I will have to start pruning, which should help water quality again by stimulating growth... talking about which... the last few days I seem to have stabilized at pH 7.0 and ORP 85, with an rH in the 22-23 range, which should be excellent, except I still have no objective way to measure if there's actually any Hydrogen present in the water, though it might be the case by reason of the Wonder shells, especially because of the Magnesium.

On Water Quality

It's one thing if you keep an aquarium, or aquariums in a house you own, you have no problem making the permanent plumbing fixes that you need to support your hobby, but it gets different in a rental apartment.

To make your own water or not 

For a salt water aquarium, you will have to, but for freshwater maybe you don't, unless you are a stickler like me. How could I not? For myself, I don't use tap water, so why would I for the fish? Personally, I use the ZeroWater filter, which does a pretty thorough job. Then I use Concentrace mineral supplement to add back the good electrolytes.
For the aquarium I use the same ZeroWater, with Seachem Replenish, to replace the necessary minerals (adjusting GH), and I may use some sodium bi-carbonate (baking soda) to adjust KH, as well as the Seachem alkaline and acid buffers, if needed. After a while, you get handy at keeping the water parameters in check.
Now that my 29 gallon tank is operational, I have plain ZeroWater in a top-off reservoir, and when I do a water change I will supply the necessary minerals, but for top off water I need only the pure zero water, since in that case evaporation leaves the minerals behind.

Since my discovery of the wealth of information on the AAP website, I began to explore using the Wonder Shell-Aquarium Mineral Block that they so highly recommend - obviously, I use the plain, non-medicated ones. Presently, I don't have long enough experience with this product to tell you if I like it or not, but the explanation made sense, so I have added it to my routine, and we'll see how well we do...

The first picture shows the basic setup. Very sparse for now, and all I have are some inverts, Malaysian Trumpet Snails, tubifex et al., seen here devouring a blanched leaf of organic spinach. There are also a half dozen of Amano shrimp around.

Starting up the tank

This time I decided to build up the tank very slowly, and I will stick with the invert cultures for a while, before I add any fish. I think I may have a little plantation of Amazon swords on my hands... So far I have not yet attempted water changes on the new tank, but I'm monitoring water conditions on a weekly basis. The wisteria in a terracotta pot is an experiment, for in the pot is some garden soil, covered with some gravel from the previous aquarium, thus providing a starter culture for healthy bacteria growth, and combining that with my very slow path of adding occupants to the tank, there will never be an opportunity for the dreaded "new tank syndrome." So far Ammonia and Nitrates consistently read zero, and nitrates and phosphates are not an issue, vindicating this slow buildup of the water conditions.
The AAP article on aquarium cycling is here, and is one of the best resources you can find. 

The only plants I have right now are easy ones that do not need a lot of light, and I use some Seachem Excel as well as a few Flourish tabs to help things along. In all, I am trying to keep PH at 6.8-7.0, and KH and GH between 100-200 ppm. Clearly, the Amazon swords are doing really well. Soon I will have a little plantation going on. All of which is fine by me, at this stage of the tank all I want is a few plants, just to grow a natural environment, and then in a while I plan to do a proper aquascaping project, once I have CO2 and serious lighting. The most interesting thing that I will want to observe is to what extent the plants and the filter compete or complement each other. Diana Walstead does her aquariums without filtration because the plants are the filter, and with heavier planting that would be true, nevertheless in my little 5 gallon nano tank, I still tend to see some nitrates and phosphate, and now I am trying to grow some duck weed, to see if that mitigates it. I also have reduced the population a bit, since moving the Amano shrimp to the 29 Gallon tank. Clearly, establishing a healthy plant life is the next most important thing after getting the nitrogen cycle started. In the beginning I'm using some fertilizer, and with increasing biological activity in the aquarium, I should be able to reduce my reliance on fertilizer - that will be a focus of my experimentation in the future.

What is most interesting about the information from the American Aquarium Products website, is the focus on ORP, oxidation reduction potential, This makes a lot of intuitive sense, since it would indicate the health of the water, and support a healthy immune system in your fish. For human beings it is known that many healing waters have extreme negative ORP, which is the reason for the popularity in certain quarters of water electrolyzers, popularly known as ionizers, to produce Electrolyzed Reduced Water (ERW). Clearly, the nitrogen cycle would cause a shift towards lower ORP, and thus healthier water. At some point I am planning to look into this more deeply.