Thread: New pond build - First pond!

Originally Posted by A.B Koi

Looking like a quality job this. Looking forward to seeing the finished article

Thanks very much. Do it right or don’t do it and all that. I’m also very much looking forward to the finished article!


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How come the BD are all at one end ?

Originally Posted by CobraKoi

How come the BD are all at one end ?

I was debating placement for ages. All my returns are at the opposite end of the pond and I didn’t want to have the closest BD pulling the lions share of the water at the expense of the other two and leaving a dead zone behind it. Because the filter system links all three BD’s and the three major pond returns - the airlifts - without physically measuring it I’d never be confident that the water was circulating properly.

I’m hoping that the BD’s being pushed to one end and the feeds at the other will give a nice strong flow down the length of the pond.


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Originally Posted by Twhitenosugar

I faced the same issue about determining what realistic flow can be achieved. I can tell you my set up to give an idea though.

I have 3" skimmer and 4" BD feeding a draco solum 16 drum. This connects (via 2 X 4" pipes) to a moving bed bio, that connects (again via 2 X 4" pipes - to ensure no bottleneck of flow) to a large water tank that I have sited my air lift in.

Airlift is about 1.7m deep, made from 110mm waste pipe. With a 2m return to the pond (top of pond return is about 15cm below the pond water level)

With a hi-blow 80xp air pump, the airlift shifted so much water that it far outstripped the flow that the drum could handle, resulting in the drum being constantly in cleaning mode

So with few bottlenecks, I estimate a 55watt air pump can probably do about 20k lph. Although that is very much a rough estimate due to the variables.

The key is big pipework i.e. 4"; as few bottlenecks as possible; a pond return close to the water level, but not above it; a nice deep air lift (1.7m - 2m deep); and an air pump that is powerful enough to constantly operate at that depth.

On my set up, I run both the air for my moving bed bio filter (210litres of k1 media) and my airlift using the Hi-blow 80xp and balance the amount of air needed with a manifold.

So basically my pond runs with 11watts background usage for the drum and 55 watts for the airlift and moving bed filter. So 66 watts.

With my UV on (comes on about 2hrs a day, I have this come on early afternoon to take advantage of my solar power) that brings consumption up to 106watts.

Not bad when some people quote 100watts + just for their pond pump.



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Thanks that’s brilliant info!!

I might have overdone the air though, I hadn’t considered the cleaning function of the drum working on a height differential. Makes sense, I’ve just never seen one in the flesh and hadn’t given the clean trigger a second thought.

My 3 BD’s run through 4” pipe work with swept bends straight to the RDF. From there they go to two bio chambers (anoxic if I can fit, K series media if not) and then to the airlifts via 3 4” pressure pipes.

I’ve got 110mm pressure to do the airlifts out of and the pressure chamber will be 140mm sleeve over the 110mm. I’ve got enough pipe to do 2m lifts but it depends on the ground I hit because it will have to be hand dug.

I’ve got a hi-blow 140 from memory - will have to check. I can always bleed air off it to my BD’s if needed, though I do have another two air pumps I purchased for that so maybe too much air in total…..


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Originally Posted by Twhitenosugar

Can you try and bench the concrete floor so that it slopes down towards the bd's.

You might be in danger of having a dead spot where crap builds up on the pond floor directly below the pond returns, if they are up near the surface.

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Good point and one I hadn’t thought of in terms of bench. I did however worry about a dead spot so I have a return from my lily pond that splits between a water blade and a 2” return - the 2” return will have a 90 on it and point vertically down the wall opposite the BD’s. My thought there is that though it won’t be a huge flow, it should be enough to push stuff towards the BD’s. If needed, I can also cut off the blade (and will do in winter anyway to stop chill) and wind the vario pump up to 40k lph to blast (perhaps too strong a word, but gently push ) anything that accumulates down there. There is a very slight gradient towards the BD’s too, but not much.

Good food for thought though! Will ruminate on it thanks


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Originally Posted by Twhitenosugar

Lol sounds like you have plenty of air!

Airlifts, set up right, can shift a very impressive amount of water.

The main restriction will be your drum filter. Say it's rated at 30k lph, realistically it will be more like 15 - 20k in real world terms (manufacturers always overstate, plus the mesh gets blocked with biofilm etc).

One airlift running at full chat will on its own probably be pushing the drum to near it's limit lol.

Anyway, as you say, you can always distribute your air across your airlifts and bleed off air (the excess air can be used for your bio filter).

Although the only issue are the valves on an air manifold are super sensitive, you will only need to make miniscule tweaks to change the flow in your airlifts.

On mine as the biofilter airstones are much shallower than the airlift, to change flow on the airlift I actually have to adjust flow to the bio filter to change the flow on my airlifts i.e. more air to the biofilter reduces air to the air lift and vice versa.

On your air lifts make sure you have 2 vents on the pond return pipework (I just used a couple of sweet T's for this). The vents will catch all the foam produced by the airlift and stops the foam entering your pond.

Are your bottom drains aerated?

If so I recommend you have them on a separate air pump to your airlifts. That way you can have them come on with a timer and also be able to turn them off without shutting down the flow from your filters.

You only need about 40lpm of air to each aerated bottom drain.

Another tip is to use smart sockets.

I use BG General smart sockets (from Toolstation, Screwfix etc). I recommend getting them... providing you can get a decent WiFi signal to your pond (I use a WiFi range extender). It means you can setup timers for each socket, change them and control everything remotely as well.



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Really useful info, appreciated.

The RDF that is top of my list currently is a 70k lph item from Burtons. I was aiming at about 20k lph for each lift.

I have 3 different air pumps so can use dedicated ones for each but and bleed to air stones if needed.

The three BD’s are all aerated. Plug timers is a great idea, but I might have to go old school segment as my Wi-Fi is awful everywhere despite having the good stuff from BT.


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Originally Posted by Twhitenosugar

No worries. I remember what it was like building my pond. So many things to consider!

Although I would caution against having anything in the pond with an edge i.e. a 90 degree elbow on your return, if you can help it.

You will almost certainly end up with a parasite infestation, (unless you set up a quarantine for them first). And they have a habit of injuring themselves on things when rubbing and flashing up against things.

I've had koi damage themselves just flashing on the bottom drains, which are relatively flat!


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I hadn’t even thought of that, thanks. I’ve never kept koi, that one never crossed my mind.

Do you think a rubber 90 would be safer? Regarding the parasites, and excuse my ignorance here, why would they take up residence in the 90? Would the water flow through it not stop them living there?


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Block work is flying up. The bottom of the window is where the block work on the front stops in the middle. The ground level will be higher as there’s MOT to go down, compo bed and slabs, so it isn’t as high above ground level as it looks at the moment.


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Also before someone points it out, the window is deliberately offset because it’s central to the patio and the pump house will potentially overlap the pond by 200mm making it square to look at


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Originally Posted by Twhitenosugar

Yep a rubber 90 would be better but you'd need to consider how to connect it? Although having no elbow in the pond would probably be better, but up to you.

The mention of the 90 elbow was more about the fish injuring themselves on it rather than it harbouring parasites



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I’ve seen some that attach by hose clip. I wouldn’t want a hose clip in there, but if it’s a tight enough fit a very tight zip tie should be enough to hold it in position and I can file the cut end flush.

Appreciate the thought - hadn’t even occurred to me pal


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It’s been really hot today. I’d planned to run my BD pipe work today but I had completely forgotten to but straight couplers, so pressure pipe work was off! I could have run it partially but it’s such an unwieldy pain in the butt I’d rather get the full length done in one go. I cut the shelf for the pipe work and ran the waste pipe you can see in the picture which is for my drain in the pump house for ease of cleaning and in case of leaks. Goes straight to a home made aqua cell, which is in the picture below filled in.

The 4” ball valves arrived too , they look good bits of kit.




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I’ve lifted the covers off the BD’s thins morning, praying that they were still full of water and thankfully they are!

The concrete ended up a little deeper than planned, so they are recessed about 20mm. I’ve mailed JBR asking if they can do me a 20mm solvent weld ring to raise the top lip of the BD’s 20mm. I think that will be fine and I’ll back fill where the guys trowelled around them with epoxy strengthened mortar.

Taking the little ‘un to the cinema and having a day off today, tomorrow I’m hoping to get the Lilly pond reinforcement in. Will get some more pics then.

Waiting on JBR for the straight couplers I forgot to order, so will get onto Jason there first thing on Monday and see what he can magic up for me.

I noticed in one of the posts earlier, I made a typo. It’s 6’ deep not 8’. That’s water depth, give or take a couple of inches.


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Busy day. I’ve got my pipe laid out and counted up, along with fittings. I’m a bit short so need to put an order in this week, not forgetting the straight couplers this time that stopped me plumbing this weekend!!



The pipe work is easily the most expensive part of this build, even the RDF isn’t as expensive as the amount of pressure pipe I’ll have got through by the end an expensive hobby this koi keeping, and I’ve not got any water or fish yet!

With the straight couplers holding me up, I did some work on the lily and goldfish pond. Got most of the brackets in and strengthening plates in. They are belt and braces, each sleeper is tied to the below by 5 1” oak dowels and 3 timberlock coach bolts. The corner stays are to give it some hoop strength. You can see the water feed in the picture below taped over with a plastic bag and the BD (not aerated but also JBR) with bricks on to stop it floating when the concrete was poured. I’ve not attached the top layer yet as I want to cut a reveal all the way around and use the cut out to clamp the liner with. That’s on the (very long) to do list!




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