How to fix eroded side walls & pump selection.

[borderfox]

Hi all. I started this pond project so long ago - it's embarrassing at this stage! Anyways, the hard work is actually done. It was dug out and then abandoned.

Question 1 - How do I go about building up the side walls of the pond again - before the liner goes in?
As it was left over an extended period, the side walls of the pond have eroded back a bit more than they should be. I'm trying to work out the practicalities of building up the side walls a little before the liner goes in. How do I achieve this?

PIC1
PIC2


Question 2 - What is the most cost effective pump that I can use in this scenario?
When I first started this project, the idea was that it would be a koi pond. Since that initial idea, the electricity price has spiraled (i'm in Ireland - we now have the second most expensive domestic electricity tariffs in Europe). Therefore, I've decided to compromise. Some folks on here previously suggested goldfish/shubunkins as an alternative. The pics above provide an indication of pond size. Can anyone indicate the most cost effective pump I could use in this scenario? I don't mind paying more on outlay on the pump - if it means its more efficient - and cuts down on ongoing costs.



If I can determine the above, at least I can take the next step and order up the liner and pump - and slowly but surely get this mini project closed out ;-)


Thanks in advance for any input.

 

[Craig58]

I think I would carve out the pond to what you need to get stable walls. If that is too big, you can maybe for example cut in a ledge or shelf down to stable soil and then build the shelf up a bit using 2" thick solid cinder block or bricks. The liner wil be covering these so you pad them well. It looks like you have a bowl shape already so is that what you were going for to begin with? I'd focus on the top edge part first and see what you can do to get a stable edge. Then from there worry about the bottom slope.

It's hard to give really good advice just from the pics and not really knowing what we are looking at and what your original plan and dig looked like. if it's been a while, much of the soil is probably already compacted enough to just redig and trim it up. Without being able to see the soil personally it's hard to say. You'll probably have to use your best judgement.

In any case, I would say that this is a pond where you want to install the liner and fill it and let it sit. Let it sit for a week or so and let the weight really settle in and fill the voids without worrying just yet about folds in the liner and stuff. Pump it out and redo the padding and fill in any spots that looked questionable and then put the liner back in and refill again. Don't trim the liner until you are sure it has fully stretched out and settled in.

As a rule of thumb, external pumps are usually more cost efficient then in pond pumps. (exceptions make the rule). I like the Artesian line of pumps myself.

Craig

 

[borderfox]

I think I would carve out the pond to what you need to get stable walls.

Yes, I would have ran with that option - but for the fact that it's just going to leave things far too tight - need to maintain a margin around the pond.

If that is too big, you can maybe for example cut in a ledge or shelf down to stable soil and then build the shelf up a bit using 2" thick solid cinder block or bricks. The liner wil be covering these so you pad them well.

That sounds like a plan alright. I guess the bricks would do the trick - as trying to somehow tack on soil/earth isn't going to be a runner.

It looks like you have a bowl shape already so is that what you were going for to begin with? I'd focus on the top edge part first and see what you can do to get a stable edge. Then from there worry about the bottom slope.

Lol - no - was never the intention that there would be a 'bowl shape'. That's come about due to some erosion of the sides over time - but won't take long to dig out again.

As a rule of thumb, external pumps are usually more cost efficient then in pond pumps. (exceptions make the rule). I like the Artesian line of pumps myself.

Ok, thanks for that. I must check out those pumps. What sort of expectation should I have in terms of electricity units expended per month with a pond of this size (with goldfish/shubunkins)?

 

[Craig58]

Can't say what the actual cost is for mine. I heard you can get devices that you plug into the outlet and then plug the device into and it figures out the acutal KW's used. But in lieu of that try some of the info on this site: http://www.lagunakoi.com/Water-Pumps-External-c-5.html

Generally the higher the Watts the more it will cost.

Craig

 

[borderfox]

Generally the higher the Watts the more it will cost.

Thanks again Craig. Did a bit more googling on this. I guess I can calculate it based on the wattage rating of the pump. The only other variables I need to figure out are the following;

1. What capacity pump will be sufficient to do the job? For instance, is this pump up to the job?

2. Does the pump need to be run 24/7? If not, how many hours is sufficient? ....OR....how do I calculate this requirement?

Again, this would be based on stocking goldfish/shubunkins. Furthermore, in this respect, the irish climate should probably work for me! (normal air temperatures reach 18-20*C in Summertime and 8*C during Wintertime).


In relation to getting the sidewalls back to the original intended points, I think I could use polyboard waterproof insulation panels to line it and fill out this space. I guess this may come in useful during the winter (although not a major problem here - but during those occasional/exceptional cold spells). Additionally, it can act as an underlay - as the 'earth' is stony/rough.


I'd be interested to hear anybodies feedback on the above.

 

[Craig58]

Interesting idea using the polyboard. Never used it or heard of it being used. But that doesn't mean you can't. I think the trick will be how to back fill it and get the liner in. I would think that with out proper back fill, the weight of the water would push in against the board and possibly crack it and push it back into weakly backfilled areas. Backfilling it might be difficult without the liner and water to hold the board in place. It might be possible to do them at the same time. Put your boards in and insert the liner. Fill with water to 6-10 inches. Adjust liner, back fill to 12-15". Adjust liner, fill water to 18-20" Back fill to 22-24" Adjust line, fill to 26-28" adjust liner.. etc.etc..

If he poly board did crack at some point because of back fill, probably not the end of world. But once filled, I would let it setlte and stretch for a couple of weeks before making my final trim of the liner. Even than, I might leave an extra 4-6" buried around the top just in case. That way, next year If you notice a section of pond wall that collpases backwards, you can unbury the liner edge and give it some slack. Than rebury it again.


The pump you link to is a 2000L/hr pump but that is at zero head. That means that every thing is basically level and you are not pumping up to a water fall. At .5m it drops to 1500L/hr and at 1m it drops to about a 1020l/hr. Even at 2000l/hr that is only 440g(uk)per hour. You don't mention the size. 4m X 4m x 1m? Just guessing from the pics. That's about 3500g(uk). The rule of thumb is to turn the water over once every 1-2 hrs. With that pump you are only turning it over about once every 8 hrs in a best case. Add any waterfall height and increases. With a 1m waterfall you are at 16hrs to turn it over.

I'd suggest at least the 3500 model and would personnally go with the 8100 model. But I don't have the electric issues you do and the 8100 model is 3x the wattage. But it is 8x times the water flow. So with the 8100 model at 0m head, you can turn the pond over in 1.9 hrs.
At that rate, you can maybe get away with running the filter for 8-10 hrs. For the 2000 model it takes at least 8 hours at 0m head to turn it over once and you'd have to run it at least 16 hours and even than it might not be enough.

With a 1m head, the numbers are even broader. The 2000 model takes 15 hrs to turn the pond over, The 8100 model takes 3 hrs. So you could run the 8100 model (110W) for 12 hrs less and get the same amount of filtration. That could save you money. Realistically you would need to probably run a minmium of 8 hrs.
8 hrs @ 110W = 880W = 2.66 turns
16 hrs @ 32W = 512 W = 1.1 turns
To get the same 1.1 turn with the 8100 model: 4 hrs @ 110w = 440W. 72 W less than the 2000 model.
Plus if you use a UV, the UV light would normally be on during this time. So you save on the UV time as well.

Of course this all assume your filtration system is desgined to handle the higher flow rates.

How often you run the pump/filter totally depends on the fish load and the filtration system. The only real way to figure out how long to have to run it is to test the water regularly. As your goldfish grow or have babies, the fish load will go up and so will the need to run the filter more.

If you plan to keep the pump off, I would plan to run an air pump when ever it is off. I'd run the air pump 24 x 7 but I know you are concerned about electric cost. So at least put it on when the pump is off. It should be much cheaper to run than the filter pump.

Most folks run a waterfall or water feature via their pumps so they want them running when they tend to enjoy the pond. So they run the pump during daylight/early evening hours and then off at night. I'd make sure than at night the airstone comes on.

But a lot has to do with your fish stocking. Goldfish will reproduce. So you will want to make sure you have a predator in the pond to keep the population down. Maybe a couple of bullfrog tadpoles should be the first thing in the pond. (not sure what is native to Ireland). Maybe a small catfish or a sunfish. If a catfish, he'll probably get big enough in a couple of years to eat all your goldfish so you might have to plan to replace him every year or two. Or, with no predator, you will have to be ruthless at some point and remove extra fish from your pond and give them away.

You didn't mention UV light. Are you planning on one? You don't mention the size. 4m X 4m x 1m? Just guessing from the pics. That would be about 3500g(uk), 4200g(US). So a 40-60W UV would probably be enough. If you run this when the filter is running in the early spring you you can usually avoid the green water. Once your plants really take off in June/July you can either reduce the time it is on, or in some cases turn it off entirely. The more plants and more surface coverage you have, the less the UV needs to be on. A general rule of thumb is to try and get about 2/3 of the pond covered by plants. Cover 100% and you can't enjoy the fish usually. Less than 2/3 you'll need a stronger UV running more.

Craig

 

[Waterbug]

1. What capacity pump will be sufficient to do the job?

If you're going to have just a few goldfish, and you don't feed a lot you probably wouldn't need any pump.

2. Does the pump need to be run 24/7? If not, how many hours is sufficient? ....OR....how do I calculate this requirement?

That's completely up to how many fish, the size of the fish, and the amount of food fed. Light fish loads don't require any pump.

You can do a trickle water change where you use a drip irrigation head like 1 GPH and leave it running 24/7. You also need an overflow to take the extra water away from the pond (which is a good idea for rain too). Is water expensive there? Trickle water change is a very good "filter". Used by top Koi keepers

If you added a stream you could just run that during the day to try and get some string algae growing which should stop your pond from going green. Streams are very good filters for even medium fish loads. Longer the better. And/or a Trickle Tower if you have any rocks around.

So there are options.

There are complex calculations that can be done for pump requirements but these are only needed for heavy fish loads and that doesn't seem to be the case here.

In relation to getting the sidewalls back to the original intended points, I think I could use polyboard waterproof insulation panels to line it and fill out this space. I guess this may come in useful during the winter (although not a major problem here - but during those occasional/exceptional cold spells). Additionally, it can act as an underlay - as the 'earth' is stony/rough.

Actually the earth helps keep temp more steady and adds warmth to the water in cold weather. The only time you want to insulate the pond is when it will be heated or in hot climates, like here, insulating the top few feet.

Going back to pumps and electric use...If you really, really wanted to get into how much power a specific pump used you have to look at what's called a "power curve". These are normally published by the manufacturer and often you have to contact them directly for the info. Some publish the data. Normally the published watts is the maximum watts. The number of watts varies by how high the pump pushes water. Not normally a huge difference but I've seen surprising differences. Again, this is only if you're super concerned about power use.

Air pumps are also a cheaper way to move water.

For the walls...you can use just a concrete collar around the top and slope the sides down. Or a short knee wall just at the top. Depends on how far you want to go. Your soil actually looks pretty stable. Used carpet for an underlayment.

 

[borderfox]

Firstly - thank you both for taking the time out for such details posts - it's very much appreciated.

Interesting idea using the polyboard. Never used it or heard of it being used. But that doesn't mean you can't. I think the trick will be how to back fill it and get the liner in. I would think that with out proper back fill, the weight of the water would push in against the board and possibly crack it and push it back into weakly backfilled areas. Backfilling it might be difficult without the liner and water to hold the board in place. It might be possible to do them at the same time. Put your boards in and insert the liner. Fill with water to 6-10 inches. Adjust liner, back fill to 12-15". Adjust liner, fill water to 18-20" Back fill to 22-24" Adjust line, fill to 26-28" adjust liner.. etc.etc.. If he poly board did crack at some point because of back fill, probably not the end of world. But once filled, I would let it setlte and stretch for a couple of weeks before making my final trim of the liner. Even than, I might leave an extra 4-6" buried around the top just in case. That way, next year If you notice a section of pond wall that collpases backwards, you can unbury the liner edge and give it some slack. Than rebury it again.

Yes, that's exactly the lines I was thinking along. I'm not so bothered about the polyboard cracking as such - it's only there to try and maintain relatively straight boundaries to the pond - and not let it push out further than was intended.

The pump you link to is a 2000L/hr pump but that is at zero head. That means that every thing is basically level and you are not pumping up to a water fall. At .5m it drops to 1500L/hr and at 1m it drops to about a 1020l/hr. Even at 2000l/hr that is only 440g(uk)per hour. You don't mention the size. 4m X 4m x 1m? Just guessing from the pics.

Your quite right - i didn't mention size. In reality, it's 3m long X 1.5m wide X 1m deep. This pic here => PIC3 PIC4

 

[Craig58]

There are people that just keep goldfish with minimum to no filtration as waterbug said. You'll need to make sure you have plenty of plants in the pond and you'll probably have a green water phase in the early spring for a few weeks until the plants can take off. You'll also have to be ruthless with population control.

Craig