Pump Size

[DigdirtJen]

When i bought the preformed liner for my pond, the folks at the store told me it held 300 gallons so i would need a 600 gph pump. The closest one they had to that was 700 gph so that's what they sold me. After i got all my supplies home, i did some research on all the supplies i bought (because I'm crazy that way ). Well the liner they sold me was not 300 gallons - it's only about 120 gallons. does this mean my pump will be too strong and cause to much of a current in the water? It is hooked up to a waterfall filter.

 

[Gilraen]

I'm new to pond-like things as well, but I know a lot of aquarium keepers recommend about 10X the container's size in turnover for one of the filters that hangs on the back of the tank, especially for bigger messy fish (goldfish, cichlids) and up to 40X for reefkeeping. Obviously don't know what you are planning to keep in the pond, but the gallons per hour alone shouldn't be too horrible. If it does end up being too much, you could maybe put some areas of plants in so that the water can't really have a straight shot somewhere to make a hard current?

 

[mrsclem]

700 for a 120 is too high a volumn. Can you return the pump?

 

[Lisak1]

Yeah, that's gonna be like a tsunami in a pond that size. By "liner" do you mean preform pond?

 

[gimpy]

Some pumps have a valve of sorts that can reduce or regulate the flow of water somewhat. You might check yours?

 

[Gilraen]

Well I am apparently quite wrong

Since my background is in aquariums, and the flow rates are apparently quite dramatically different, what is the rationale for keeping the flow rate so low in a pond?

 

[mrsclem]

2 1/2 total volume per hour turnover seems to be the norm. Too much rapid water can tire out and stress the fish.

 

[Phaewryn]

I have a 1200GPH pump on my 60 gallon pond with a 8" wide waterfall (with about 3' of total drop). I added a T splitter and about 3/4 to 7/8ths of the water goes to a waterfall that's got about 3' of rise while the rest runs a little mini fountain in the pond. The water is moving a lot, but the plants and fish seem to be doing do fine (plants are in planters on shelves or planted in the margins of the waterfall tiers and fish are fancy guppies). You can't have plants that need still water or fish that don't like swimming into current, but mine is working out fine. The main questions you need to answer for us to tell you are
1. How wide is your waterfall weir?
2. How many GPH is your waterfall box rated for?
3. How much total rise will you have from the pump to the waterfall box?

Waterfall boxes are not a popular/common option in this forum, most people here choose bog filters. When using a waterfall box, though, your pump must be at least 100 gallons per hour for every inch wide the waterfall weir is and that will be the absolute minimum, so you'll need more if you want a nice sheet of water falling from it. Many ponding sites say a better rule is 1000-1500GPH per every inch of waterfall, but that's for BIG waterfalls. I think mine is about right at 1200GPH for my 8" wide waterfall box. Waterfall boxes are rated for their maximum GPH throughput. Tell us what brand yours is and measure it and we can tell you what GPH it will handle without overflowing (mine is rated at 900GPH but handles 1200GPH fine). We also need to know how high up your waterfall is above your pond and how long your tubing is.

The way I figured mine was 100GPH per inch of weir (800GPH since my weir is 8") + the volume of water in the pond x 2 (150GPH) + 3' of head (my pump had enough lift so I didn't have to factor in extra GPH for that). I looked for a 1000GPH pump, but got this 1200GPH pump cheaper, so added a T splitter so I could split the water volume going to the waterfall if the box overflowed, but my experience is that this will never happen, and the flow is actually about right without the fountain. When the box prefilter is dirty, the flow can even be too low to drive enough water over the falls to keep it from trickling down the rock face. I can shut the fountain off and the waterfall is still no where close to overflowing, or even impressive, IMO:

Here's a video of my pond/waterfall today. 60 gallon pond, 1200GPH pump: definitely not too much GPH for this waterfall box!

 

[Phaewryn]

Since my background is in aquariums, and the flow rates are apparently quite dramatically different, what is the rationale for keeping the flow rate so low in a pond?

Pond fish are apparently very delicate? A lot of people here use bog filtration, not waterfall boxes, and perhaps don't know the math involved in pushing waterfalls? My pump GPH is 16X my pond's volume. I can't have plants that need still water (like mosaic plants), but then neither is my pond breeding mosquitoes. I don't actually have an interest in "pond fish" like goldfish or koi though (I keep fancy guppies in my pond in the summer). Someone who knows why pond fish can't tolerate moving water when aquarium fish can will surely respond.

 

[Jhn]

As mrsclem mentioned most pond fish (koi and goldfish) don’t come from rapid moving aquatic environments, but much slower moving ones, which is why too much circulation can cause them stress.

Where your pond/aquarium inhabitants come from needs to be taken into account when setting up any ecosystem ie most reefs are extremely dynamic environments. Also, generally speaking fish tanks are much smaller than outdoor ponds, in order to keep up water quality, more circulation is needed so waste/detritus can be kept in suspension to be removed by the filter system.

If I went by freshwater fish tank rules would end up needing a 100,000 gph pump on my pond, which would make it look like a whirlpool and would hate to see the electric bill on that pump.

 

[Phaewryn]

If I went by freshwater fish tank rules would end up needing a 100,000 gph pump on my pond, which would make it look like a whirlpool and would hate to see the electric bill on that pump.

I don't think I'd equate my pond turbulence to a whirlpool, but there is certainly a lot more flow in my pond than in my indoor aquarium. Luckily I suspect my pond pump is on my landlord's electric bill. The circuits in this old house are not right. I know my microwave, air conditioner, half my lights, and the outlets in two rooms are on their circuit (because when the breaker blows, I have to ask them to turn it back on since it's not in my panel). The flip side is that I might be paying for their microwave, air conditioner, or washing machine and dryer. It's nice to not have to worry about the electric cost of the pond though (especially when I heat it in the winter).

 

[Lisak1]

Pond fish aren't "delicate" - in fact, koi are actually native to rivers and enjoy a current to swim in. I think @Jhn hit the nail on the head - aquariums are so much smaller that they require more filtration. Plus many don't have live plants to add to the biological filtration that a pond has. And the point about the size of pump you would need if you translated aquarium rules to pond rules is also important - you'd have to put massive pumps on an average sized pond. Just one more reminder that the only thing ponds have in common with aquariums is they both have water.

@Phaewryn I think everyone here is aware of the math involved in choosing a pump. Whether we have bogs or waterfall boxes, we all had to choose an appropriately sized pump. But the kind of turbulence you have in your 60 gallon pond would be amplified dramatically in a larger pond using the same "math". If you did have fish, you'd never see them. There's something very lovely about the waterfall falling into the smooth, glassy surface of a mostly still pond. Water lilies don't like being splashed either, and who doesn't love seeing a the pads and flowers of a gorgeous lily on a pond?

 

[Gilraen]

Interesting perspectives. Thank you, everyone! Sorry to have derailed your post, Jen.

 

[Phaewryn]

@Phaewryn I think everyone here is aware of the math involved in choosing a pump. Whether we have bogs or waterfall boxes, we all had to choose an appropriately sized pump. But the kind of turbulence you have in your 60 gallon pond would be amplified dramatically in a larger pond using the same "math". If you did have fish, you'd never see them. There's something very lovely about the waterfall falling into the smooth, glassy surface of a mostly still pond. Water lilies don't like being splashed either, and who doesn't love seeing a the pads and flowers of a gorgeous lily on a pond?
[/QUOTE]

Yeah that makes sense. I hadn't considered if everything scaled up at the same rate, yeah, that would be a massive waterfall. I bet my waterfall and pump would work for a pond 2-3 times the size of my current pond.