lancashire,
United Kingdom 
Hi everybody. It has been a while, 9 months to be exact.
I've been too busy but now seek your advice.
I am digging out a garden pond and am going to use a liner. So far so good, but, I will need a feature and have had a thought.
I have a cast iron fire pit, about 18" [450mm] diameter, which stands on legs. My idea is to have that in the pond sticking proud of the water by about 6" [150mm] and to feed water in from underneath so that it flows over the rim and back into the pond.
My question is
The cast iron will rust. As the pond is going to be several thousand litres, the rate of rust will not discolour the water, but will the rust upset or kill any wildlife which will inevitably live in the water. I do not intend to keep exotics or Koi, but to have purely natural wildlife. Frogs, newts, sticklebacks, snails etc.
Your comments will be much appreciated.
Many thanks in advance.
SouthportSmith
27 Apr, 2014
Answers
Won't it tend to discolour the water? I'm thinking of streams contaminated with iron that are bright orange and not very pretty. If you want to throw money at it you could have it powder coated and then it wouldn't rust at all. and you can have a choice of colours, at least black green or grey.
28 Apr, 2014
It takes a huge amount of iron to discolour the streams that you describe, Stera. In rural area is due to ploughing through the iron pan in the soil by agriculture or forestry practices; in urban areas by polluting industries, now fortunately rare.
29 Apr, 2014
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A small amount of iron in the water will not be detrimental to wildlife. Think of the amount of iron, in the form of discharge pipes, piling, and fly tipping, whilst unsightly, a small amount does no harm. Make sure that you clean the ash etc from the firepit first.
27 Apr, 2014