Carp Lake Management – Using Lime

David writes;  I had this Email sent to me by a French lake owner today… I thought I’d pass it on so other lake owners could either benefit or comment;

‘I recently had a meeting with a recognised fishery expert and we had a very interesting conversation about the use of lime.

how to look after a carp lakeIt is already widely known that lime kills undesirable water-borne creatures and I’ve been adding lime each winter to achieve this.   However, having fully discussed this with the vet, it is more specific that just spreading dry (granulated) lime over the surface of a lake.

I’ve been told that it’s necessary to make up a “lime milk”.   This is done by mixing the granulated lime 1 part to 3 parts water.   This makes a “lime milk” which should then be added to the lake (by means of some type of Heath Robinson system – pump etc) and spread throughout.   This turns the water a milky colour, which will disperse.  The timing is also important – this should be done in February (the guy said before March) but I’m assuming that the hatching of creatures is dependant on whether one has a warm or cold spring.

The difference between just adding the dry lime and the milk solution is that the dry lime simply drops to the bottom and only kills the larvae there, whereas the milk solution also kills the suspended larvae that are waiting to hatch. The dosage rate is 150kg of lime to 1 hectare.

I thought perhaps you may find this information useful.’

(Definitely worth reading the comments below before you come to any conclusions on this one)


9 thoughts on “Carp Lake Management – Using Lime

  1. Chas says:

    We, too, have been adding lime in winter and have a couple of questions which we hope can be answered by someone out there. Is granulated lime preferred over powdered lime because there is a bagged powdered lime here in France which is recommended for ponds? Will liming in this way have the same beneficial effect on a lake which has a river running through it because we mix the lime in the inlet which disperses it through the lake?

  2. Chris says:

    Hi Chas,

    Lime has a very low solubility in water, less than 2g per litre, so when you mix it with water you are making a slurry which disperses through the water column. Whether to use powder or granules depends on how fast the river flows through your lake, if it looks to be fast then use the granules otherwise stick with the powder.

  3. David says:

    Just been sent this comment in from a carp fishery owner by Email;


    The blog provides poor and mis-guided information. For full details and specific use of ‘lime’ you would have been better off providing the link to the U.K’s sole distributor of Siltex. where real world use direct from the supplier provides the correct information for this product, unlike whats been posted on the blog.

    Having had experience of applying this product and the results, what has been ‘bloged’ is incorrect, hope this helps.

  4. Martin at Oakview says:

    Thanks to everyone for the info so far. The original comments were mine so please continue to shoot me down if I’m wrong.

    My research on liming started with the Siltex recommendations and I then added other comments from fish farmers and French fish vets, so I guess that this will be where my information differs from Siltex.

    I’m hoping that we can end up with what we believe to be a common approach to this issue. So far, I’ve found only one thing that everybody seems to agree on – that regular liming is beneficial.

    It does appear that satisfactory results can be achieved at a fraction of the cost of Siltex.

  5. Chris says:

    Just to clarify something, it would be a shame to be talking cross purpose.

    Siltex is a proprietry brand of finely ground Calcium Carbonate (chalk) most often prescribed for silt reduction and general improvement of lakes and ponds.

    Lime is Calcium Hydroxide most often prescribed for pH control and reduction in phosphate levels and for the reasons introduced above. It will also have an effect on silt. As a stronger alkali it will need more careful handling and dispersion.

  6. David says:

    A comment from the Forum post on this subject;

    I have never used lime but it sounds as though it works… but would be worried about what it does to the insect life that you want. Also I have no idea of the price of lime. It would take a 150kg here at La Bletiere and that sounds a lot of lime to go in… and it’s also the “look” after the dosage has gone in, but I suspect it will soon clear.

    When we lived in England I kept koi and had a 6000 gallon pond which I used to add salt to in the spring and autumn – this did the same as the lime. In the 6000 gallons I added 20kg of salt and that was enough according to the experts.

    The one big advantage the salt has is that it kills all the blanket weed it comes near, but not other plants. It also gives the fish a good clean through.

    After about 1 day all the blanket weed in my pond would be in the vortex ready for dumping. Might be useful for any of you that own a pond and maybe one day I will try the lime.


  7. Lee Johnston says:

    I have heard of lakes being drained dry and then being treated with hydrated lime (calcium hydroxide) to sterilise the lake bed before refilling, I was told a long time ago, never add it to the water with fish in it as it is so strong that if incorrectly dosed it can raise the ph so quickly that all the aquatic life may not be able to cope with the rapid change. I’m guessing treating the lake empty would allow you to check the Ph of the water before adding fish back in. I would be a bit wary of this stuff.

    Calcium Carbonate (chalk) or even better (calcium magnesium carbonate) are well known for treating lakes and are probably a far safer option for a lake owner.

    I know prevention is better than cure so in looking after our lakes we regularly test nitrate, nitrite, heavy metals and of course ph levels. And if weed looks like its becoming a problem, add a few herbivores i.e. Grass Carp.

    I’m afraid my philosophy on this one is; If it’s not broke, don’t fix it! Or get an expert to look at it.


  8. jon marshall says:

    After having done a fair bit of research on this it seems that liming is only necessary when the PH drops below 6.5 therefore considering my lake is generally between 7.8-8 I have never felt it necessary to do it, and each season I have fantastic growth rates and an abundance of natural food
    As previously said “if it ain’t broke…….

  9. emma jackson says:

    Hi, we have a clay based pond in dorset which is heavily silted. I’m doing work to the sides and have been offered a load of quarried chalk to build up the banks. I’m hoping that use of this would help with the water clarity and not harm the residents of the pond, namely some grass carp and a large quantity of newts, toads and frogs. Would love any advice.

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