Working Vegetable Filter in your Garden

What is a vegetable filter? ... Its mid-summer; the fish in your pool are really active, they are healthy and growing, you are feeding them everyday and the sun is out and everything should be just koitastic. But it aint. You know the fish are there, but the water is so green the best you see are ghostly green shadows at feeding time with a flash of whiskery jaws.

You know what the problem is, it is nitrates, not harmful to the fish, but it causes the algae to proliferate so much your filter and U/V system cant keep it clear. After all the algae are bound to multiply. They are plants and nitrates are pure rocket fuel for plants.

So would it not be not only logical but also biological to get plants on your side in there in the water to munching up the nitrates before them bleepin algae get to them? Yes it would. All you need to do is call in what they call higher plants, which are basically plants that are bit more sophisticated than your average algae and preferably more greedy, and with greed comes vegetable muscle.

Now when we are talking muscle in the plant world, the best crew for dealing with this situation are not the sort you want to have direct access to the water, because they would undoubtedly take over and you would have a worse problem than the algae. It would be like inviting the local chapter of the Hells Angels for a drink at your sophisticated soiree; you would be asking for trouble.

You need these guys as bouncers at the door! And so let it be with the heavy weights of the water garden. These are essentially plants that grow fast, so have them nicely confined in a container and let the fluid contents of the pool flow through their roots systems. Working in conjunction with the normal micro flora you find round the root hairs and in the bottom of ponds, a lot of those undesirable nitrates will be just taken out of the water and absorbed by the plants.

Not only that, any soluble toxins or pollutants will be extracted. Factories, mines and breweries have all taken advantage of using this capability of plants.

All human waste, tin, lead and even radioactive uranium can be extracted from water as long as the root hairs of these plants have access to the water. In large domestic situations and controlled industrial applications, using plants in this way, they are referred to as reed bed systems and for a pond or pool Im calling it a vegetable filter.

The Vegetable Filter

The common reed or Norfolk reed, Phragmites australis, is the top performer in these filters, because not only has it got a phenomenal growth rate in the right conditions, but also obligingly oxygenates the water as well; essential for many of the bacteria that need oxygen to sustain them. Other plants that do well in my books are Water Cress, Rorippa nasturtium-aquaticum, although it succumbs in very polluted water, Bittercress or Cardamine praetense and Fools Water Cress, Apium nodiflorum, which loves alkaline water. 4: Water cress: Rorippa nasturtium-aqauticum.) 5: Bittercress, Cardimine praetense) 6: Fools Water Cress, Apium nodiflorum; the rampant root run is revealed, sprouting at virtually every leaf node.)

Is it Easy to Add to my Setup

Its as easy or difficult as you wish to make it. If you already have a stream, or waterfalls with header pools, you can place aquatic baskets planted up with cress or reeds in strategic places. In fact any plants that are easy to keep in order will help. Keep an eye on them in order to stop them from seeding or running adventitious shoots under your rockwork. A regular cut back ensures they are kept working producing new growth most of the season. 7: In the header pool to the waterfall I found Villarsia, Nymphoides peltata, a useful vegetable filter. You can see the clarity of the water in the pool below.)

If you have a relatively small pool and you would like to buy a proprietary product off the shelf in kit form with everything you need, then there is the Oase Filto-Fall, which is a basic kit for processing the water in a 2 cubic metre pool. All it needs to work is a pump that will turn over 5000 litres per hour, which needs a power supply and hose, and of course half a dozen clumps of Norfolk reed.

/ 8: Oase Filto-Fall . It is designed to sit embedded into the ground on the edge of a pool or at the top of waterfall or stream. Water pumped up from the pool will enter at the front base of the tank- note the hole for a fitting in the bottom /front- and rise up through the plants and cascade into the header pool. Because it rises up in the tank from pressure from the pump, it could not be incorporated in an existing filter system unless it was of the pressure type like the Hozelock Bioforce or the Oase Filtoclear filters.)

Build Your Own Vegetable Filter

Oase Filto-Fall would cost you in the region of 50 or 60 and may you do want to incorporate a veggy filter into your present system and or your pool is bigger than 2 cubic metres. You could try building one. If you had an old filter tank, it may cost you nothing, or at least just the cost of a few bags of inert gravel and some plants. An old Blagdon style filter tank. These came in a variety of sizes; for a vegetable filter, the larger the better. For starting from scratch, notice the inlet and outlet fittings and also how the interior divisions are put together.)

The parameters you are working with are to try to circulate half the volume of the pool water through the system every hour. Also, in order to give the water a thorough treatment, the surface area of the system wants to be approximately one third that of the pool. This is an ideal that is out of the question for many people and since a min-reed bed system is very often an add-on to a biological filter system, it may often be the case that not only is anything is better than nothing, but it proves to be quite adequate.

Small to Medium Pools

Any large container or series of containers that will hold water and to which you can fit outlet pipes to will do. A large old filter of the basic Blagdon type where water feeds in a the top of the tank, goes down through some filter brushes and up through filter medium to flow out back into the pool would be perfect. However any waterproof container can be adapted.

  • Take a waterproof container (a domestic header-tank is perfect) and glue with silicone or hot glue gun a profile that will fit inside to make small compartment 10cm wide that will be the settlement chamber. There needs to be a 5cm gap between the bottom of the divider and the bottom of the tank.

  • 10cm wide strips of plastic glued into place between the profile and the inside wall of the container act as braces and supports.

  • A filter medium support plate is made from a sheet of plastic drilled with holes.

  • Glue 5cm wide strips of angled strips of plastic on the underside of the filter medium support sheet. These will help support the sheet from sagging when the weight of the filter medium is pressing down on it.

  • The container itself is drilled with a hole-borer attachment to an electric drill. A 40cm hole is made in the front to take the 40mm waste pipe fitting that will make up the outlet. Another 25mm at one end of the new small settlement chamber will take the standard 25mm hosetail fitting that will be the inlet.

  • With the filter in position and the fittings and support plate in place, the main filter chamber is filled with coarse inert (not limestone) gravel to 10cm short of the outlet. This is topped of with smaller gravel to just below the outlet.

The same procedure would be adequate for a DIY biological filter except that the medium ought to be an Alfagrog or hortag.

Oase Filtofall.

The tank is placed in position and the shape is cut around the shape and a hole is dug to a depth at which the container protrudes about 10cm from the ground. A little sand is put in the excavation to help with the final levelling of the unit. The unit is set in level with a spirit level. 10).

With the unit in place, the protruding edge is disguised with rocks and soil. Aquatic baskets can be used in your filter container, or the whole thing can be filled with rough gravel on top of the base plate. This Oase Filto-Fall has a custom made basket that is placed in the tank. 11)

The Rough gravel, 32-25mm, is poured in up to about 10cm below the top edge and levelled out. 12 )

On top of this, smaller gravel (or in my case an expanded clay filter medium) is poured in on top level with the top edge in the Oase Filto-Fall but below the outlet on you homemade version. Norfolk Reed (Phragmites australis) is divided up and planted in the top medium. 13)

Switch on and keep running 24/7. 14) 15: This Oase Filto-Fall sits at the top of a waterfall).

DIAGRAM 4)A larger system could also be devised from a series of filter boxes or domestic loft header-tanks. Alternatively, you build filter chambers out of concrete blocks laid on a 10cm concrete slab, rendered on the inside with fibre-reinforced cement and sealed with a tanking slurry like Vandex. These would be simply a tank, or even a series of tanks built one above the other, with the water pumped up from the pool, flowing from top to bottom. At its simplest, the supply of water comes in from a series of pipes distributed along the back edge of the top tank, and would trickle down though a planting of reed in inert gravel (15-30mm). I would prefer the trickle up solution to the trickle down method, but the former method would require considerably more engineering, by having to pipe the water from a collection or settlement chamber, into and below the planted chamber in order for it to rise up and overflow into the pool or the next filter bed.

When Can you Expect Results from Vegetable Filter

The system will start mechanically filtering straight away, but allow at least a month in the growing season for all the plants and the micro-flora to get established. Even when there is very little plant growth in the winter, there should be a certain amount of biological filtration from the bacteria in the gravel. Switch it off in very cold weather; you will just have to hope that everything holds its breath. The algae do tend to find a window of opportunity briefly in the spring since they can grow profusely at much lower temperatures than many of the higher plants, but once summer is in full swing the algae haze is soon dealt with.

How much does it Cost

It is worth experimenting with what you might have lying around. If you already have a multi-chamber biological filtration system, it may be just enough to plant up the last chamber in the series of tanks. If you only have a submersible pump supplying water to a waterfall, then the main expense is over. Incorporating a vegetable filter or mini-reed bed at the top can just mean the expense of a header tank, a sheet of HDP or ABS plastic and two cheap plumbers fittings maximum 30. As for the plants they are the cheapest. If you live near rhymes, dykes or waterways that are constantly being dredged on a rotational basis, then common reed, scraped out by the ton, can be rescued by the handful. Gravel is generally less than 2 a bag if you choose the cheapest inert cracker grit.

Tools

The tools you would need if you were starting from scratch with a basic plastic or fibreglass tank:

A glue gun or a silicon glue and dispenser.

A power drill with hole borer attachment for the outlet pipe, which should be a minimum of 40mm. You will also require a holeborer of the size for the inlet hole, which should be adequate for the hosetail, which in turn should fit the tubing from the pump.

Timewise, even constructing from scratch, the large header tank method of building will take less than an hour to build and probably 2 hours to dig in and fit up.

The number one Tip for getting it Right

Let them at it!

Above all, get the right plants for the job - the common reed. A decent quantity planted 15cm apart, being fed water from the pool 24 hours a day, 7days a week.

Maintenance

Just cut the plants back at the end of the year (more if it is Cress or such like). If there is a drain plug accessible on the tank, backwash on an annual basis. Otherwise dig out, divide the plants and replace the gravel every 4 to 7 years.

Published with permission of Peter May, for more visit ... http://www.perfect-pond-detective.com/