I received the following enquiry today via e-mail. As we know, koi and carp are the same species. Anybody who can give some inputs?

I have been living in Cape Town for the past 4 years and have
struggled to find anywhere that looked safe to fish for carp (not
koi). So I have built a pond in my garden and am struggling to
maintain it properly due to lack of knowledge. I have about 18 carp in
the pond plus a couple of barbell and blue tales as well. The fish
look and act O K but am concerned that I have not got the correct
saline levels and that the fish look red around the gills. I would be grateful if you could advise me in order to overcome my concerns over the welfare of the fish and the maintenance of the pond. The pond is roughly 50,000 litres with 2 pumps creating waterfalls for oxygen but as the pond is for fishing there is no filtration or cleaning system.

Kind Regards
Tony Pegg
PS I am currently living in Constantia

I have found that my bigger fish over 75cm do show some gills on the edge of the gill cover. Hope you know what I mean.

Op die rand van die kiev deksel sal 'n rooi / pink lyn wees.

Whether it is koi or carp, or whether they are in a pond or natural mud dam, the principles are basically the same.

The salt levels should not be more than 0.2% over an extended period although they can tolerate a salt contents of up to 0.5% (for short periods)

Your salinity levels should be between 0 and 0.2% and can be tested with salt test kits readily available, alternatively with an electronic salt meter.

As for other parameters, your should test the following on a regular basis, especially because you do not have a filtration system in place.


Ammonia
less than 0.1 ppm(depending on temperature)
Nitrites
less than 0.2 ppm
Nitrates
less than 50 ppm
pH
6.7 -8.5
Alkalinity
60 - 170 ppm
Hardness
75 - 150 ppm
Chlorine
less than .04 ppm
(You probably have a borehole in which case it is obviously not neccesary)
Oxygen
more than 5 ppm

These can all be tested with a standard test kit available from pet shops and koi outlets. They are going for approximately R 250.00.

Should your Ammonia or Nitrite levels go beyond this, your dam can not handle the fish load without filtration, in which case you should either lower the load or obtain some sort of biological filtration.

I believe that the red on the gills may be caused by stress due to high Ammonia or Nitrites and I do not believe that salinity is the problem.

My suggestion is to test all the above.

> Hi Paul Thanks for the info.
>
> I quickly popped out to the local Koi shop but they only had strips to test water and the results were as follows:
>
> Nitrites 0
>
> Nitrates 0
>
> PH 8.4
>
> Alkalinity 80
>
> Hardness 75
>
> I used my pool test for Chlorine and it was 0
>
> I have two pumps for waterfall/ cascade so should be plenty of oxygen and the dam has been in operation for over a year before I put the carp in.
> My son mentioned that the last carp he caught, last weekend, had red fins as well as red gills and a mark on it's side( could not remember colour or size of the mark).
> Does all this point to a parasite rather than a water problem???

Hi Tony

I am a bit worried about your PH. Although Koi/Carp can tolerate up to 8.5, it should not be above 8 and it might be your problem. If a system does not have a biofilter, the PH tends to go up. PH are measured in exponents of 10. Yours are almost 10x the recommended level.

Do your perhaps have lime leaching out of cement? or rocks or a source of Calcium that causes the high PH.

To rectify, you will probably have to do more water changes, alternatively you could use peat or chemicals, although I am not fond of any chemical way of adjusting PH. Sharp fluctuations of PH are far more damaging than a high PH.

If it is parasites, you will probably see the fish jumping/flashing, but the ideal would be to take a scrape.

By the way, I have about 6 big carp full of eggs and a very big Tilapia for free if you are interested to add to your collection.

Hi Paul
Thought I would update you.
I put some fresh water (borehole) and immediately the PH level dropped
so it looks like there is lime leaching somewhere. Checked again this
morning and PH 7.5 and stable from yesterday.
It appears that the borehole water is at 6.2 PH and having entered the
pool it increases which I guess may mean emptying the pond and
sealing it.
Caught one of the fish and it had a couple of scrape marks on it's
side and its eyes were odd in the sense that it looked as if it had
the start of cataracts if you know what I mean but fought like hell
and it swam off annoyed but happy.

My ammonia level is around 0.2. How can I decrease this?

Various options:

Water changes
Feed less
Increase your filtration
Add bioboost
Decrease fish load
Add zeolite to your filtration

Thanks

Hi Cam0
What is your pH - in the morning and in the evening?
How long has your filter been running?
Regards,
Chris

One more question -
What is the turnover time of your pond?
Another question how many koi and what size?
Chris

I have not tested pH of late because the shop was out of stock of the test.

Last time I did check it was fine.

Turnover is about once an hour I would imagine (8000l/h submersible).

Pond is small at the moment - 3000 litres with a submersible pump ;/

I have 9 koi, all are about 10cm +- and 1 is about 25cm.

Pond has been running for about 7 months I think.

I'm changing the pond soon though.

Cameron

Hi Cameron,
The pH has a direct bearing not only on our koi but on the nitrifying bacteria in our filters.

These bacteria prefer and function better in alkaline conditions - i.e. 7.5 - 8.6 pH.

Below pH 7 (neutral) they are battling and at about pH 6.5 they are not doing there job of converting ammonia to nitrite to nitrate.

Regards,
Chris

Great thanks