Natural Filtration 301 Chapter 6
Streams and Active Upflow Bogs
Let’s agree to talk about planted streams in the same section as Upflow Bogs, even though the water in the stream is passing sideways, sort of, through the gravel. The idea is the same; pumped water is actively flowing through planted gravel beds, carrying nutrients and well-oxygenated water directly to the roots of plants. With the key ingredients of nitrates, phosphates and oxygen in place, plants respond with explosive growth, usually thriving and often exceeding “normal” sizes. As a quick example, this photo shows Iris pseudacorus, listed by USDA as having leaves 40” long, suggesting a typical maximum vertical height of three and a half – but the I. pseudacorus pictured, in an Active Bog Island, has leaves seven feet long!
Active Bog Filters are especially useful in ponds overstocked with large Nishiki-goi (Japanese Carp or Koi), which produce prodigious amounts of ‘excretory nutrients’, shall we say? Nishiki-goi also tend to destroy any plants they can get access to, so planting in pots is a losing battle. Active Perimeter Bogs can offer an easy solution to the problem. When first building the pond, just widen a shelf anywhere along the stream or edge that will end up about 8” deep, place a generously sized pipe that’s slotted or perforated on the shelf and cover it with 6-8” of gravel. Plant up the gravel and run water through the pipe and you have an Active Bog. It’s almost as easy to add an Active Perimeter Bog to an existing pond that needs additional filtration. You basically need only overlap a flap of liner anywhere along the edge and ensure that the water finds its way back into the pond. Once you find a spot along the edge where a bog will fit, it’s relatively simple to plumb a slotted or perforated tube, place it on the flap so that water will flow back into the pond, cover it with gravel and plant it.
What if the edge isn’t going to work for your application? Maybe it’s already landscaped or hardscaped, or there just isn’t enough room? There’s another option, an Active Bog Island, right in the middle of an existing pond. In fact, the Iris above was planted in one of the more successful installations I’ve seen, an Active Bog Island that was added to an existing Koi pond that had outgrown its Active Perimeter Bog. As the Koi grew larger and more numerous over time, the original Perimeter Bog just wasn’t large enough to process the additional wastes, and the rest of the perimeter was already landscaped. The builders came up with a novel idea – to add a bog to the middle of the pond, sacrificing almost no volume of water but adding shade, circulation, refuge – and doubling the Active Bog area. Like all the best ideas, this one is simple. Four columns of stacked cinderblocks painted black were set on a level area of pond bottom, supporting a fiberglass grate 8” below water level. The 4x8 grate was trimmed to an irregular shape and covered with a piece of liner so the gravel wouldn’t fall through. A perforated pipe set on top of the liner was plumbed to a 1200GPH pump sitting on the bottom under the platform. Stones were dry stacked around the edge of the platform to hold 8” of gravel covering the pipe, then the gravel planted with Iris pseudacorus and other marginals. When the pump is turned on, water flows out through the roots and gravel and stones and back into the pond, stripped of nitrates and phosphates and crystal clear, even with 5 lbs. of food a day feeding 250 8” Koi! Excess food and fish wastes are converted to nitrates right at the roots, turning the gravel bed into a plant superfactory. This is exactly what happens in Hydroponic systems, or more properly, Aquaponic systems, where organic nutrients from fish are pumped to the root systems of crops, so it should come as no surprise that many terrestrial plants including vegetables, not just marginal aquatics, thrive in these bogs, and giants are the rule, not the exception. 40” Iris leaves stretch to 7 feet tall, cherry tomato plants grow to the size of Yew bushes, Taro becomes a shade tree. As more and more people become aware of the possibilities, we’ll see a shift from separated vegetable gardens and ornamental pond areas to integrated gardens where water features and kitchen gardens are integrated, even inseparable – you heard it here first – but that’s a story for another time. What’s most important for pondkeepers is that these bogs pull all the nutrients out of the water column, starving out single-celled and string algae, and rendering the water clear and clean.
Let’s agree to talk about planted streams in the same section as Upflow Bogs, even though the water in the stream is passing sideways, sort of, through the gravel. The idea is the same; pumped water is actively flowing through planted gravel beds, carrying nutrients and well-oxygenated water directly to the roots of plants. With the key ingredients of nitrates, phosphates and oxygen in place, plants respond with explosive growth, usually thriving and often exceeding “normal” sizes. As a quick example, this photo shows Iris pseudacorus, listed by USDA as having leaves 40” long, suggesting a typical maximum vertical height of three and a half – but the I. pseudacorus pictured, in an Active Bog Island, has leaves seven feet long!
Active Bog Filters are especially useful in ponds overstocked with large Nishiki-goi (Japanese Carp or Koi), which produce prodigious amounts of ‘excretory nutrients’, shall we say? Nishiki-goi also tend to destroy any plants they can get access to, so planting in pots is a losing battle. Active Perimeter Bogs can offer an easy solution to the problem. When first building the pond, just widen a shelf anywhere along the stream or edge that will end up about 8” deep, place a generously sized pipe that’s slotted or perforated on the shelf and cover it with 6-8” of gravel. Plant up the gravel and run water through the pipe and you have an Active Bog. It’s almost as easy to add an Active Perimeter Bog to an existing pond that needs additional filtration. You basically need only overlap a flap of liner anywhere along the edge and ensure that the water finds its way back into the pond. Once you find a spot along the edge where a bog will fit, it’s relatively simple to plumb a slotted or perforated tube, place it on the flap so that water will flow back into the pond, cover it with gravel and plant it.
What if the edge isn’t going to work for your application? Maybe it’s already landscaped or hardscaped, or there just isn’t enough room? There’s another option, an Active Bog Island, right in the middle of an existing pond. In fact, the Iris above was planted in one of the more successful installations I’ve seen, an Active Bog Island that was added to an existing Koi pond that had outgrown its Active Perimeter Bog. As the Koi grew larger and more numerous over time, the original Perimeter Bog just wasn’t large enough to process the additional wastes, and the rest of the perimeter was already landscaped. The builders came up with a novel idea – to add a bog to the middle of the pond, sacrificing almost no volume of water but adding shade, circulation, refuge – and doubling the Active Bog area. Like all the best ideas, this one is simple. Four columns of stacked cinderblocks painted black were set on a level area of pond bottom, supporting a fiberglass grate 8” below water level. The 4x8 grate was trimmed to an irregular shape and covered with a piece of liner so the gravel wouldn’t fall through. A perforated pipe set on top of the liner was plumbed to a 1200GPH pump sitting on the bottom under the platform. Stones were dry stacked around the edge of the platform to hold 8” of gravel covering the pipe, then the gravel planted with Iris pseudacorus and other marginals. When the pump is turned on, water flows out through the roots and gravel and stones and back into the pond, stripped of nitrates and phosphates and crystal clear, even with 5 lbs. of food a day feeding 250 8” Koi! Excess food and fish wastes are converted to nitrates right at the roots, turning the gravel bed into a plant superfactory. This is exactly what happens in Hydroponic systems, or more properly, Aquaponic systems, where organic nutrients from fish are pumped to the root systems of crops, so it should come as no surprise that many terrestrial plants including vegetables, not just marginal aquatics, thrive in these bogs, and giants are the rule, not the exception. 40” Iris leaves stretch to 7 feet tall, cherry tomato plants grow to the size of Yew bushes, Taro becomes a shade tree. As more and more people become aware of the possibilities, we’ll see a shift from separated vegetable gardens and ornamental pond areas to integrated gardens where water features and kitchen gardens are integrated, even inseparable – you heard it here first – but that’s a story for another time. What’s most important for pondkeepers is that these bogs pull all the nutrients out of the water column, starving out single-celled and string algae, and rendering the water clear and clean.
