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How to Install a “Veggie” Plant Biological Filter

If you haven’t done so, Read: understanding the Veggie/ Plant Biological Filter

Okay, now that you have some information on natural plant (Veggie) biological filtration for your pond, how to you put legs on it? Before we get started, let’s review the takeaway from the last article.

Benefits of a Natural Plant “Veggie” Filter

water hyacinth
  • Maximum Surface Area for Bacteria Growth
  • Nutrient Uptake into Plant for Algae control
  • Reduces Need for Algaecides
  • Eliminate Need for Damaging UV Filter
  • No Need for Expensive  Bead Filters, Bio Falls
  • Minimal Cost
  • Home to Invertebrates for Balanced Ecosystem
  • Less Maintenance
  • Aesthetically Pleasing
  • Nothing to hide (fake rock top, Bead Giant)

Picture of the Perfect Biological Filter in Action

water_hyacinth_roots plant bio filter

There it is!

I created a small retention pond (10% of total pond volume) between my main pond and top waterfall, about 18” deep. I covered the liner with a non woven geotextile fabric for protection (one underneath as well). I added six inches of pea gravel sized river jack on top of the liner. Then I through in five water hyacinths and watched them divide like a weird science horror movie..., finished!..., almost.

Bog Filter Anyone?

How do you make this awesome bio filtration system even awesomer? You add a bog filter (my next article) at the same time. You already understand the science from the last article understanding the Veggie/ Plant Biological Filter. The gravel that I mentioned above works off that science; it is yet another medium for water to move though, creating a second beneficial bacteria breeding ground. What else? The gravel on the shallow perimeter shelf is used as a root anchor for more aggressive plants that grow hydroponically (soil less), yet do not float on the surface. Hence the water Iris in the above photo..., more nutrient uptake, more natural surface area (roots), more aesthetic value as well.

How do I Maintain a Veggie Bio Filter?

Veggie Plant Biological filter Maryland

Do what this guy just did. When the frost comes, pick up your hyacinths and throw them away. It will be sad to trash such a great friend, but unless you live in the tropics, you must say good buy. Don’t let them die off in the pond (see previous article).

You may have to thin out your water hyacinths during the season. You have given them a phenomenal growing environment and they will thrive like bamboo. Don’t be alarmed, this just means your system is working well. They literally just lift right up. You may have to pinch off a few Siamese twins but it’s very easy.

Iris pseudacorus 2
Iris pseudacorus plant filtration system

What if I want Bio Filtration in the Winter?

Why? Fact- most bacteria will not survive the winter temperatures. Your fish have shut down and are no longer polluting the water (You aren’t feeding them are you!?-BAD!), and bio filtration is unnecessary. Most people disconnect their bead filters over the winter to protect them from freezing and cracking. Many also shut down their waterfalls to prevent problems as well.

If you insist on a winter bio filter I have the best one for you, and yes it is natural. One, if you build your pond like we suggest, you already have one. Remember that river jack pea gravel, (bacteria home), water moving through media? Alone it’s not as good as the “Veggie Filter”, but it’s plenty good enough for winter.

If you’re a maniac :) and you want to have a winter plant filter, you can actually build one. I’m giving up all the secrets here. Enter Iris pseudacorus (shown on left). In lieu of water hyacinths, you can use this fantastic plant, with a little ingenuity. This Iris will live with it’s roots frozen solid.

Get yourself a few milk crates, set them in your collecting pool with the tops about 2”-4” below water level. Buy some iris pseudacorus plugs & set them on top of those crates about 12” apart, and push roots trough the crate holes. Take some string or light gauge coated wire and tie the roots to the crate. Shebang!, you now have a year round “Veggie” filter.

You will want to prune off the foliage in the winter because the Iris will go dormant, but the roots will still be there as a useless winter veggie filter :).

How Well Does a Veggie Filter Really Work? For Real?

I’ve been installing ponds based on this technology for over twenty years. I’ll take a well designed natural plant filtration system over a mechanical bio filter any day. Don’t get me wrong, I use bead filters & such in certain applications, ie... ridiculously high fish loads, ponds without waterfalls, etc., but they cannot cover the ground that the “Veggie” filter can.

Case Study

I created the system shown at the top of this article in a commercial application in Davidsonville Maryland years ago. It is part of an elaborate koi pond, stream, and multi level waterfall feature that we installed at no charge as an advertising display. The owner is a pond supply company. We originally installed bottom drains, a large bead filter, a UV-filter, 2 external pumps and one submersible pump. He was continuously dumping barley pellets into the pond and stream trying to control a constant algae problem (no luck).

Long story short, he left everything running throughout the winter, and cracked his UV, and bead filter. He didn’t replace them, even though he owns a retail supply store. (Not the best businessman). I told him I could take care of it another way.

We added the water hyacinths and Iris (river jack was already there), and watched the pond system transform in short order. The water became the clearest it had ever been, the ammonia levels- perfect, nitrate conversion was fantastic, the expensive show koi were as healthy as could be, and the algae disappeared.
Irony-The broken equipment is still there, doing nothing but looking useful, and is probably used to sell similar equipment.

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