Filtration, the simple approach

Posted by Bill Putnam on

When considering equipment, most start out with what they are told will work and it's often very cheap and simple. Typically a waterfall filter is what many start out with yet to rely on just the waterfall filter falls in-line with the phrase, you get what you paid for. Some find the maintenance of cleaning the waterfall pads to be simple. Some may not even recall it requires maintenance and forget to do it. Soon they find themselves with pore water quality, green water and possibly even fish health issues.

Subersable pond pump costs more to run than a good external pnd pump           External pond pumps save money over submesable pond pumps





Its typical that people starting off with a waterfall filter purchase an inexpensive submersible pump that draws higher amps in electricity. It seems at the time to simplify the install. The benefit in a higher costing external pump that draws less amps then a submersible pump would result in paying less each month to the electric company and thus warrant the additional upfront expense. Paying less each month easily pays for the upgrade to an external pump that will also last 2 - 3 times longer than the submersible pump.

Better Filter

Some pond owners will up the budget sooner or later and spend around $1200 for a bead filter thinking that they now are on the right track and are going to be OK. While it is true this is better because it does mechanical trapping of crud and performs biological with the very important feature of easy back-washing, they soon find out that they should have spent another 30% and bought a name brand bead filter that will outperform, polish the water better and last easily 20 years or more. The GC TEK filter below is an example of a well made leading brand filter that will last.

GC Tek Alpha One Pond Bead Filter  Click here for GC Tek Filters...

GC Tek AlphaOne Bead Filter

Clearing up Green Water

Upgrading to a nice bead filter will not however keep your pond from turning green. This is best handled very simply by purchasing an Ultraviolet Light (U.V.). The U.V. is best installed after the filter to trap the debris from the water which then permits cleaner water for the light to make better contact with all the water passing through the U.V. chamber. (See the diagram below showing the equipment setup)

W Lim Pond UV Light Sky Hawl

 W Lim Sky Hawk U.V. Click here to see the Sky Hawk Series

Purchasing a U.V. Light that is ideal for the size of the pond requires some factors to be taken into consideration. Total gallons, pond depth, pump flow and amount of direct sun on the ponds surface. Ideally, ponds should be over 3 feet deep. The deeper the better when considering not growing lots of Algae and making it easier on the U.V. Light. The brand selected can make a difference also. The typical amount of power a U.V. puts out is measured in watts. A pond less than 4,000 gallons may be able to use a 40 watt U.V. unless the pond is shallower than 3 feet or located in a very hot climate. Often it is best to over size. It is advisable to replace the lamp every year because they get weaker and weaker  even though it is still glowing.

W Lim UV HO Lamp Power Graph compairing Emepror Aquatic, Delta UV, Aqua Ultraviolet UV

One brand of U.V. Lights has taken the power and strength of their lamps to a new level. Most brands all use a lamp that produces 30,000 microwatts. W Lim Corp High Output (HO) units produce 80,000 microwatts. This extra amount of power benefits the pond owner in many ways. Its not only producing better kill capability in clearing water and pathogens better, it is also going to last longer. Third party testing proved the output and that after 16 months, it was still producing 80% power output. Other brands all require the owner to replace the lamp at 13 months because it has reached the 60% level that is starting to to be too low to prevent green water. W Lim also installs the HO lamps in their economical and well built series of U.V.’s called the Sky Hawk.

W Lim Dragon Pump, Bead Filter & Sky Hawk

Basic Filtration Categories

Mechanical - The trapping of large and small crud or debris and separating it from the water.

Examples - Skimmer basket, Pump basket, pre-filters, settling chambers, filter pads.

Biological - The filter that has media and the ability to process the Nitrification or conversion of chemicals naturally from the aquatic life in the water and chemicals from other sources breaking down.   

Examples - Waterfall filters, pressurized filters like bead filters, up flow or down flow chamber filters that may be open or closed systems with media.

Ultraviolet filtration (U.V.) - The use of a U.V. Light and or chamber containing a U.V. Light that is targeting the correct light spectrum to kill algae and or sterilize pathogens or bacteria in the water as it passes over the Quartz sleeve protected U.V. lamp.

Example - UV Filters often can be enclosed into a all in one filter type  body, yet often those units are more ideal for very small ponds less than 1,000 gallons. U.V. Chambers that have an entry and exit port can range in wattage's from a single lamp 8 watts to multiple lamps that can be large enough for municipalities (City drinking). Most ponds use sizes ranging from 40 watts to 150 watts. Ponds that are over 25,000 require higher outputs and multiple lamp units. 


Suggested simplified pond filtering equipment layout setup:

  • Skimmer to clear the surface and prevent leaves and debris from sinking to the bottom
  • Bottom drain intake
  • A 3-way valve to connect the Skimmer and bottom drain lines to one external self priming pump intake
  • External Self Priming pump with built in basket
  • Quality Bead Filter
  • Quality U.V. Light sized for your flow rate and pond size
  • Waterfall or stream return to pond that adds aeration

This top down view of plumbing diagram has control of the source water using a 3-way valve from the skimmer and the bottom drain. Next is a SkagiTek True Pre-filter that has a stainless steel basket to trap crud prior to the pump. The pump output connects to the bead filter that then goes to the W Lim Sky Hawk U.V. Light. When the U.V. is installed vertical, the water should enter the low port and exit the upper port to return to the waterfall or pond as seen in the above diagram. (If your UV body is laying horizontal, then point the ports up and entry and exit ports selection is not important, just be sure that the end with the power cord can be accessed for replacing the lamp with the needed clearance to add and remove it.)

TIP: When considering building a pond, consider an aerated bottom drain and get a 40 liter air pump. The air rising up from the bottom drain will bring water from the bottom and create a flow across the top, then down the sides and result in sweeping the crud laying on the bottom to go to the bottom drain that the pump is sucking water from. This makes your pond a self cleaning pond for crud on the bottom. (The air pump can be on a timer for 2 hours early in the day to make it easy to see the fish the remainder of the day). If your pond is already built and you would like to have a retrofit bottom drain with aeration, click here.


A phrase that is often passed around pond owner forums; you can never have too much filtration!

Bringing you clear solutions,

Bill Putnam





Share this post

← Older Post