Hi all,

I am a garden center manager who has recently taken a new position where they have ponds (which I have never had before) and I have a general knowledge of ponds but not sure what the right thing to do in this situation is.

I am in NH (zone 5) and we have a pond which had been covered for most of the winter with a tarp (bad I know, I didn't do it, hehe). Yesterday on my day off for no good reason some employees took it upon themselves to remove this cover. First let me say that the pond does have a heater in and is not frozen on the top. My biggest concern is that there is a pump that is running and it is positioned about 4-6 inches over the surface of the pond-I think it may have been placed lower but someone moved it because they were concerned about aerating the pond. Today the fish are all swimming.

It was always my understanding that pump should be removed in winter or at least positioned not to disturb the water in the bottom

The pond is aprox 5x4

All that being said here are my questions:
Does a pond have to have a pump for aeration? I know plants make air of which there are none in pond this type of year. Can oxygen be taken from the open water surface with no pump?
What is the best way to help my fish survive? (Recover the pond or don't)?
Should I keep the pump running and if so what is the best placement to avoid cooling the bottom water? I haven't looked at the gpm but the one running now is a fairly strong one...so what would be the max size pump I would want?
Also if anyone knows-does algae need light to survive? One of my employees is challenging me to keep the pond open because there was some algae buildup in the pond-I don't know what the condition of the pond was in fall-I wasn't here-so if you could tell me about algae action in winter that'd be great too.

Thanks in advance for any advice is GREATLY appreciated!

First of all welcome to the board! :)

You say the pond is 4'x5' but how deep it the pond and does it have a waterfall?

It does have a waterfall but that pump was disconnected/removed in the fall. The pond does vary in depths-at it's deepest it is about 30-36" deep.

I live in Zone 6/7 and leave my pump and waterfall going all year. See my winterizing page at http://www.fishpondinfo.com/winter.htm for more on the pros and cons of keeping the pump running. In Zone 5, I normally suggest to turn off waterfalls but a small pump near the surface can be used to help with aeration. Aeration is vital in the winter as, if there is ice cover, there is less gas exchange. An air stone can sometimes keep a hole open as well as a de-icer with the benefit of adding oxygen. I have both aeration and a de-icer in my 153 gallon pond and the waterfall going in the 1800 gallon pond.

A tarp over the pond will help keep it warm but it is dangerous if it prevents gas exchange.

Aeration can be created from a pump that just outputs or goes to a fountain or waterfall. Aeration can also be created from an air pump which is simpler and very effective.

Without aeration, there is less gas exchange at the surface but, as long as there is an opening, there will be some gas exchange.

In the summer, plants under the water produce oxygen during the day but actually use it at night so a pond with tons of plants can have low oxygen overnight, enough sometimes to kill fish. Thus, water movement and aeration are a good idea every day of the year.

At this point, I would not put the cover back on the pond. A cover should only be used it if it elevated above the water's surface and has outlets for gas exchange. An aerator of some sort is really also needed when a cover is used. It's late enough in the winter that you shouldn't need the added protection of a cover now.

Unless the pond is over 3 feet deep, the cooling of the bottom layer is really not a concern. My winterizing page has more on that. You can set the pump about a foot below the surface and have it broil the water there for aeration and water movement. Elsewhere in this forum, I have discussed with others, including KK who lives in the coldest place on earth that has an outside koi pond, that it's better to have water movement to add oxygen and prevent stagnation to worry about the temperature stratification in the water of shallow ponds.

For a pond of about 300 gallons (assuming your pond is 2 feet deep, that's the volume), a pump running around 700 gph is good. I prefer to turn over ponds twice an hour, especially smaller ones. Experts often say to turn over every two hours but that's really not enough to keep ponds in good shape. I have a 700 gph pump in my 153 gallon pond and a 2600 gph pump and a 700 gph (summer only) pump in my 1800 gallon pond.

Most algae will die in complete darkness. Some light will get through most tarps. Read over my pond algae page at http://www.fishpondinfo.com/plants/algae2.htm

Good luck!

Robyn- Thanks so much for all that info it was super helpful!

I have a small ( about 300 gph ) pump sitting maybe 10 inches from the surface on a ledge-arms length from the surface. The out-take hose is short and wedged under some rocks on the side of the pond. This way is keeps a strong current ( breaking the surface for oxygen ) and the smaller fish aren't sucked to the pump as easy. Last winter I must have peeled off at least 5, this winter it was 3--with only one death resulting. I also ran a de-icer at nite ( only a few daylight times this winter )..and that worked well/ especially being on a remote control. :D I prefer the heavy landscaping netting myself. As the new boss ( and your point-of-expertise is not ponding ) you need to ask your experienced employees ALOT of questions/ especially opinions. You need to work with the one that's challenging you...are their opinions being ignored ( and they know what they're talking about) or they just don't like that part of their job, which you can work together to make the maintaince of the pond physically easier. You need to change those strong feelings from a challenge into an asset.
As for algae, my pond right now is getting a nice layer of 'fuzz' covering everything and water is totally clear. It'll look like a velvet carpet when it's fully alive and it's a kick to watch the fish all line up and nibble off the walls...sorta like a massive veggie snack bar. As for string algae, goop it out and throw in the nearest flower pots..makes good fertilizer. If the pond was pea soup...too much sun, need more plants or just a small wattage UV light on a small independent pump does wonders for algae and bad bacteria in the water.
OH, and welcome to the board. :D This sites THE best, and Robyn is all-time queen of info...but the rest of us put our 2 cents in when she's busy. :rolleyes:
Now we even have a Centerfold celeb in our miss ( wayne r )..hehehe :P
Some are more experienced ponders than others, you can take a look on Robyns Showcase pages to get an idea of what we're about. But beware April...ponds are kinda addictive.....you'll be planning your own by mid-summer. :blink: :D