Koi Forum • 3800 Gallon L shaped concrete pond with window : Your Pond Build

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Hi guys and girls!

I used to be quite a regular member on here and have built 4 ponds already in the past, but after finishing uni I moved back to my mum’s house temporarily and put my fish in her pond (which I had to extend because of the number of fish video here for anyone who might be interested

but I was only there for about 9 months before I bought my own apartment and the fish obviously had to stay put.
I was in that apartment for about 12 months and I then bought another house, but this time it was a 4 bedroom detached place with a garden which we moved into almost 18 months ago. We’ve spent the last 18 months working on the inside of the house and put in a huge 3,000 litre coral reef tank (again, for anyone interested there’s the build thread here – http://www.ultimatereef.net/forums/show … p?t=542991) but it’s now time to start on the garden, hence starting this thread :-)
As I said, I’ve got some experience of pond building already but we are planning on doing this one in concrete and this is why I have a few more questions, as all of the other ones have been liner ponds. The basic plan is an L shaped pond, 3.6m on the two longest sides of the L and 1.8m on the other sides and 1.8m depth. 1.2m of that will be below ground, and 0.6m above ground so we can have a window, and the decking will be raised on the other side to the same level as the pond. Lastly we want stepping stones going over the pond so we were thinking about putting in a concrete lintel about 3/4 of the way up the pond and building the piers from that to support the stones.
One quick thing RE the budget – at the moment I have no spare money to do this project as it’s all gone on the house renovations in the last 18 months, but my mum is looking to move out of her house soon and is keen to close the pond down so it’s easier to sell. This means that realistically we need to complete this project this summer before it’s too cold to move the fish, and she said she is able to lend me around £5,000 to get the job done. Do you think this is a realistic budget to get the pond up and running, even if it doesn’t include unnecessary things like the facing bricks? We already have the pumps and filtration sorted so the £5k will be for the physical pond build alone.

Now, firstly my questions!

Obviously the base needs to be concrete, but I’ve read that it can either be regular concrete reinforced with rebar, or fibre reinforced concrete without rebar. What are people’s opinions on these options, and any idea of the difference in cost? Is 6″ depth enough or should it be 10″? Is it OK to pour the concrete base onto aggregate straight on top of the soil or does it need extra treatment?

Is it overkill to build the below ground walls with hollow blocks reinforced with rebar and concrete, or would regular blocks suffice? (Perhaps backfilled with concrete?)

Bearing in mind we need to try and keep the costs down, what is the cheapest way to EFFECTIVELY waterproof the walls? We don’t want to do a bodge job and I know fibreglassing is the ideal way to do it, but honestly how bad are waterproof renders/sealed renders?

Do we need two bottom drains (almost half way along each section of the L) or would we be OK with just the one in the centre of the L? If we are going to have two bottom drains, do we need to ensure we have the same length of pipe to each after the Y section where it splits to get an even flow from both, or is it not a big deal really?

The pond is almost at the lowest point of the garden so we will need a way of draining the waste water from the Nexus 300. We have drainage points in the garage already for the fish tank (as the sump is out in the garage) but to get the water from the pond to the drain it will obviously need to be pumped. What is the best way of doing this?

We’ve already had one guy round for a quote but if I know exactly what is entailed then I will know what is and isn’t needed on the quote and possibly even do some myself to cut down on the spending costs.

I think that;s all the questions for now, but there will obviously be more to come! Any advice would be much appreciated :-)