Frequently Asked Questions
What size pump do I need?
The size pump you need depends on the flow you want, usually measured in gallons per hour, or gph, and the height that you want to bring the water up to, measured in feet and called the head height or Static Head. Pumps are rated by gph at a given head height, so if you want 2000 gallons per hour falling from a 3’ tall waterfall, you’ll need a pump that does 2000gph @ 3’ of head. A flow chart will show you what the pump you are considering will provide throughout its range. For the greatest efficiency of water moved per watt and the longest life for your pump, choose a pump that will run near the middle of its range when your requirements are met,. For example, for the waterfall above you might choose a pump that is rated at 3000 gph at 0’, 2100 gph at 3’ and has a 10’ shutoff.
How do I know what flow I want?
A simple rule of thumb for waterfalls is to use the appearance of the falls as your guide to flow. If you will be satisfied with a trickle of water that breaks up into many small rivulets or ribbons of water as it falls off a sharp edge, you will need 50 gph per inch of width of falls, so a 12” wide waterfall will need 600 gph for a trickle. For a clean sheet of water off a sharp edge you need about 100 gph per inch of falls, so you’d get the water to sheet off the same 12” wide waterfall edge with 1200 gph. For the appearance of a LOT of water flow, you’ll want about 200 gallons per inch, or 2400 gph falling over that 12” wide waterfall.
How do I know what my Head Height is?
There are 2 parts to the answer. First, the Static Head in a system is the height in feet from the surface of the water the pump is sitting in to the highest point it is pumping to. It doesn’t matter how deep the pump sits in the water, since it is only working when it is raising water up from the original level. Next, the friction or resistance added by the pipe and fittings the water must flow through is the Friction Head, which is added to the Static Head to get the Total Head. You can keep your Total Head as low as possible, maximizing the flow from your pump, by keeping the friction losses in the plumbing as low as possible, usually accomplished by using as large a diameter pipe and fittings as possible.
What size tubing do I need?
Generally speaking, the typical back yard water garden has a low Static Head (see above), that is, the waterfall is usually between 1’ and 10’ in height. If your pond falls into this category, you can take advantage of very efficient MagDrive and HY-Drive pumps which require very little electric to produce great flows at low heads. The catch is, you’ll want to move the water through relatively generous pipes or tubing so your pump is just lifting the water to your falls without having to work against a lot of friction in the plumbing. These are the recommended maximum flows per given diameter of pipe so your pump is just lifting water, not forcing it through restrictive plumbing.
What kind of pump do I want?
The type of pump you choose is going to make a big difference in your electric bill, so you’ll want to choose carefully. Simply put, it can take 4 times as much power to double the volume of water pushed, but about 8 times as much power to double the pressure, or Head Height, the pump is capable of, so for the sake of efficiency you’ll want a pump that only produces the volume you need at the Head Height you need. Using a pump that can push water up 45 feet when your waterfall is 3’ tall is going to cost a lot more than is necessary. Once you know your desired volume and your Total Head (remember to use large tubing to keep friction losses low!), choose the type of pump that does the job for the least wattage spent. For low and medium heads, MagDrive pumps are the most economical choice for flows up to 1800gph. HY-Drive pumps are even more efficient than MagDrives in the 2000-6000 gph range, sometimes saving half the electricity compared to big MagDrives, and both are MUCH more efficient than high head Direct Drive pumps, which typically cost 4 times as much to run in the 1800 to 6000 gph range, but offer much greater head heights. If you need the high pressure these Direct Drives produce, because of restrictive plumbing, or very long runs of pipe, or for very high waterfalls, or for tall jets of water in a fountain, then choose a Direct Drive. If you don’t need those high head heights, you’ll save money using a MagDrive or HY-Drive pump.
Why is my water green?
This is the most common question in ponding, the easiest to answer, and the hardest to”fix”. Green water is caused by free-floating algae cells in the water, as opposed to the types of algae that colonize the bottom and sides of the pond. All algae growth happens simply because there’s sufficient sunlight and lots of plant food in the water. All plants feed on nitrates and phosphates, but algae reproduce so quickly that they can “bloom”, reproducing exponentially and causing green water.
How do I keep the water from turning green?
All you have to do is remove the nutrients, and the algae will subside. The algae themselves do a great job of removing nutrients, so spring blooms common in cold weather climates typically subside by themselves. This is because nutrients build up all winter and the first plants that can take advantage of them are the algae cells in the top layer of water as it starts to warm up in the spring. They’ll consume all the available nutrients and subside in a week or two. During the rest of the season, algae blooms are usually caused by overfeeding or runoff. You’ll want to eliminate these sources of nutrients first. Only feed your fish what they can completely consume in a few minutes. Any more is algae food. Make sure no runoff is getting into your pond, not only to keep fertilizers out but pesticides, fungicides and other toxic chemicals as well. Grass clippings can be a major culprit if you have to mow around the perimeter of your water feature. If you still have green water you may not have enough ornamental plants to consume the nitrates that are a natural end product of good biological filtration. Consider adding pond plants to consume the nitrates and, if possible, shade the surface of the water with their leaves to remove another key component of algae growth – sunlight. With about 60% of the surface of the water covered with lily pads or floating plants, alga just can’t thrive. We do NOT RECOMMEND algaecides. Killing the algae cells just provides more nutrients in the water for the next bloom, and it will just be that much bigger.
How do I add pond plants to my Koi pond, when they just eat them all?
You can almost always add plants to your filters where the Koi can’t get to them. If that’s not possible or not enough plants will fit in the filter(s), consider adding an Active Bog, a shallow gravel-filled planting area at the perimeter where water pumped in from the pond flows through roots that pull the nutrients from the water column, effectively starving the algae. Since you pump the water into the bog it can be placed anywhere where the water will flow back into the pond, around the perimeter or even on a floating or fixed platform in the middle of the pond (Bog Islands), and your Koi can’t easily get the plants. Look up ‘Active Bogs’ on the Web for further information, or contact us here at Danner
Should I use a UV Clarifier to control algae?
You can use ultraviolet light to control floating algae, by pumping water through a tube containing a UV light source. UV light at the appropriate wavelength and exposure actually damages the DNA of algae cells, preventing them from reproducing effectively. Since individual cells typically only live a few days, they die off by themselves without reproducing, so the water clears. HOWEVER, the use of UV light to control algae can mask an underlying problem. If you have too many nutrients in the water and not enough plants to consume them, you WILL get string algae instead, which, since it doesn’t float, won’t be affected by the UV light. UV is most effective when used for those spring or Indian summer algae blooms when the other plants in the water garden are dormant.
How much water should I flow over my UV?
Just enough and not too much. Easy, right? On the contrary, this is a very tough question. To clarify, or control green water, the recommended dosage is 15 microwatts per second per cubic centimeter of water at a frequency of UVC of 265 nanometers. Whew! What this boils down to is a formula for the right amount of sunburn. You don’t want to incinerate the cells, that would take too much energy, you don’t even need to kill them, just to stop them from reproducing, so there is a maximum recommended flow rate that ensures that the cells passing through the light will get enough of a ‘tan’ to make them sterile (hence the term UV Sterilizer). Too fast a flow means not enough exposure and hence, no effect on the cells. Our UV’s are rated, therefore, by the maximum flow that will still provide for enough exposure to the light to be effective. It follows that you can make a light more effective by slowing the flow, thus increasing exposure time, so we often recommend a Valved Bypass [insert link to Valved Bypass instructions] to selectively flow only part of the water going to the falls through the UV, to maximize exposure rates. However, and this is the tricky part, if the flow is too slow and not enough pondwater is being exposed quickly enough, the algae can reproduce before they make it into the UV. This sometimes happens in larger ponds with lots of nutrients and sunlight, and generally requires multiple UV units for effective control. The point is, do not exceed the maximum flow rates recommended or your UV just won’t work, and decreasing the flow will typically make the UV work better.
How often should I replace the bulb?
UV bulbs are rated in hours of effective UV emission, after which their output is too low to control algae. Our bulbs are designed to provide at least 60% of their original UVC output at 9000 hours, at which point we recommend replacing them. 9000 hours is a year’s use, and most ponds need UV the most in the Spring, so we recommend replacing the bulbs once a year in the Spring for 100% output when you need it most. Bear in mind that the bulbs still produce visible light after a year, so they will still appear to be working, but their output at 265 nanometers will be low enough to render them ineffective for algae control.
