Monday, June 16, 2008

Advice for starting a new fish pond

As we move into the year I often get queries from visitors at my web site about how they should set up a pond and whether they need a pump and filter. The following is a typical example, and my response:-
Hi Jim - Hope you dont mind this email but, Ineed your advice, I have a pond approx 1.50m x 1.50m and approx 1m deep. I have built this myself and I am now at the stage where I need to put a filter and a pump in, but can't seem to get the right advice, everyone telling me different ways, and the fact that i am a female is no help - they try to sell me items I just know are either to expensive or bigger than I need. After reading your site and looking at your bio-filters I am now wondering if you can help me, I hope to keep a small number of fish in the pond but thats another stage that I need to look at later, in the mean time any advice will be most welcome.
Many thanks.
Here is my response:-

That sounds like quite a small pond, and if you're having just a few small fish in it, (goldfish, golden orfe, shebunkins, etc, but not carp which can grow too big), you may not actually need a pump and filter system because the pond will probably be able to obtain its balance on its own. A small fountain may be all you need to aerate the water. Unless of course you've built it with a waterfall? In which case you will need a pump.

Its only if you put too many fish in it, or feed them too much, and then have too much sunlight on it that you might have trouble with green water, or poor water quality. Blanket weed is nearly always a problem at some time of the year regardless of what you do, but a well balanced pond
suffers from it less. A pond is a man-made (or in your case woman-made!) enclosed environment, and if you put too much "life" into it, which creates too much by-products in the way of poo and ammonia because you fed them too much, and don't have enough plants to use up the excess nitrates produced by the bacteria in the pond (nitrification cycle), then you're gonna have to give nature a helping hand by adding a filter!

So I would suggest patience is the key. See how it goes on its own for a start (no pump or filter). Don't buy expensive fish just in case your pond isn't right and they die. Get some bacteria culture added into the water to get things building up the natural good bacteria in the pond. The fish
pee ammonia, which the bacteria can get started feeding on, and so the cycle begins. Add a few nice pond plants, lilies, marginals (shallow water), water hyacinths (these are great because they float on the top, and naturally prevent too much sunlight going into the pond, and can be easily removed if they grow so much as to cover the pond - which they do!). I use Bio-Claire Pond Conditioner bacteria (see

Just don't overfeed! I just give one full handful of fish food pellets in the morning and one in the evening. I have about 20 fish in my pond, two of which are ghost-koi each about 1 foot long. Far too many for my pond really! But they keep having babies. The fish will feed on other life in the pond as well, e.g. shrimps, larvae, algae, etc. So don't worry about them starving.

Kids love to feed fish, and this is often where the problems start, they feed too much. The uneaten food will drop to the bottom and rot, producing food for phytoplankton (the little buggers who turn green in the sunlight, so giving you green water). The more food the fish eat the more they will excrete ammonia - fish pee thru their gills when they breath. This is what the bacteria feed on and turn into nitrites and nitrates (fertiliser). Pond plants like fertiliser - so do phytoplankton!

So take it slow and easy to start. See how the pond copes with the summer as it is. Add a small fountain if you like for effect and to help move and aerate the water. Moving the water helps regulate its temperature in summer, and oxygenates it - warm water doesn't hold oxygen so well, and this can make the fish gasp for air at the surface. I think that us guys like to play around with our equipment (ahem!), and can't help ourselves building pipes and waterfalls and filters and all that. I think you should just do it in your own way, and not be brow beaten into buying the latest big-bucks filter.

Unless I am totally wrong and you are more ambitious? In which case the only thing I have always recommended is not to go cheap on the pump. A decent solids-handling pump will run for years, and if its well-designed with a big plastic cage around it then it won't block up with weed too quickly. My Titan 8000 litres per hour runs for 2 or 3 months between me hauling it out to clean it. The power of the pump is important too, but this depends on whether you will have just a filter, or a waterfall as well.

Too powerful and it will push water thru the filter so fast the bacteria will say, hey here comes dinner, whoah, um there it goes, as it swoops past them. The water needs to go nice and slow through the filter. But if you've got a waterfall then you want it to look like a nice fall of water that gives some sound, not just a trickle. Thats why I use a ball-valve to split the flow two ways from the pump, one to the filter, one to the waterfall and I can adjust them just right. 8000 lph would likely be too much for your pond. Maybe 4000 or 5000 would be better.

Anyway, I think thats probably stuff for the future. Live with your pond first, see how it goes for a few months. If it starts to get murky, very green or the fish seem unhappy get a water test kit to check the pH and ammonia levels aren't becoming too high. If they are then it means the natural plant life and bacteria balance in the pond aren't able to cope, and you've reached that point when its time to consider adding a small sewage treatment works - yes, a bio-filter, then you can try building something like I've done, or buying one from the shop if you're not DIY inclined.

So first relax, let nature do her job and only if she can't manage will you need to intervene. Keep it simple and natural to start.

Good luck

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At 18/7/08 1:38 pm, Blogger chris said...

Hi Jim,
What a great site and such easy plans for the filter. I have made a slightly larger version closely following your excellent work. I used a five and a half foot plastic water butt in the shape of a terracota grecian urn with lid. I included the vortex, then a layer of large filter brushes, then japanese matting, then a large air difuser on top of the matting then Kaldnes K1 as a moving bed. The results have been far better than I had hoped and the water looks good enough to drink (almost). My only problem is the pre filter. Where did you get the narrow hollow pipe for the spacers? Smallest I can find is 22mm which slows water down considerably and has also caused top and/or bottom of the pre filter tube to blow! I can provide photos of the filter if you want. Thanks again for your truly helpful site.

At 18/2/09 5:53 am, Anonymous Daniel C. said...


This is some really great information!

Hope you don't mind if I pass it on to others!



At 11/11/09 10:39 am, Anonymous James said...

I'm just starting a new fish pond and have been trawling the net for some useful information. There's a lot of useless info out there, but I have struck gold with your blog! I will definitely be coming back here for more tips and advice. I would love to hear your thoughts on blanket weed control as this is an area that interests me a great deal.


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