English Koi

[glolite]

Hi guys, have been on the tropical site a few times as a newbie and got loads of help with my new hobbie. However, we've had 2 ponds for a few years. One is a wildlife with frogs, newts and plants etc., the other is less planted with gold fish, golden orfs, roach, rudd and some English Koi which we got from a friend. It's a large pond, 5f wide 12 ft long and 6ft deep wll mature. Our friend gave us 7 Koi and they did wellthrough the spring then one died. We tested the water all fine except low O2 so bought a pond pump (it is oxygenated anyway). The pump comes on twice a day for 15 mins. We then lost 3 more fish, one after the other even though the oxygen levels were fine. They all went in mid summer when it was hot (remember?). The other 3 are fine. I wondered if anyone can shed some light on this problem as I really don't want to loose the rest next summer.
Thanx in advance.

 

[ryan]

How is the pond filtered? Its unlikely to be low oxygen levels even though hot weather can cause this as Orfe and Rudd have very high oxygen requirements and would be the first fish affected. Were the any signs of disease before hand? Marks on the body, gasping at the surface etc?

 

[Cat]

I thought you had to keep the pump on all the time we do and had no deaths.

 

[ryan]

It depends on your stocking levels on how long you need to leave an oxygen pump on for if at all. Ours is on all the time just to keep the water circulating and so we can always be sure it is oxygenated.

However, re-reading your question - 15mins does seem a short time to leave it running for, the oxygen it produces in that time won't make much of a difference in a pond stocked with Orfe, Rudd, Roach and Koi unless it is very powerful.

 

[glolite]

Thanks for the replies. The pond is filtered by an all in system which contains a pump and norm pond filters plus UV filtration. So I suppose that pump is on all the time. The extra pump is a hefty beggar designed for pumping out drains etc it produces a a very strong current. (Hubby's just informed me it's a submersible with a 1.5 inch outlet). The oxygen level always rises after coz we tested. The fish that died were gasping at the surface and I forgot to say that it was just before a thunderstorm which I read can cause oxygen depletion. One fish only had a fine slime on him almost like a fine, jelly net. Other than that no others showed disease in fact they looked beautiful making it even sadder

 

[ryan]

Fish gasping at the surface is normally a sign of nitrogen pollution, either Nitrites or Nitrates, were these readings ok?

One fish only had a fine slime on him almost like a fine, jelly net.

Sounds like a disease called skin slime, this does affect koi and is quite hard to treat. It is normally caused by poor water conditions which break down the slime coating of the fish leaving them open to parasite attack. I don't think it would be oxygen depletion as the Orfe would be the first to suffer the affects, Orfe require such high oxygen levels that it is illegal to move fish over a certain size, same with Grass Carp. Unless the Koi were alot bigger than the Orfe?

 

[glolite]

Yes, the Koi are bigger than the golden orfs. which are about 4 inches. The Koi are big at about 12 inches. Is it illegal to move Koi aswell? If so, how big? We tested the values and ammonia/nitrites both nil. PS my hubby reckons the pool dimensions were way out and are more like 25feet long by 12 feet wide. I'm not good at estimating ponds

 

[ryan]

As the Orfe are smaller the larger Koi would have been more affected by the oxygen levels. Any size Koi can be transported as they're oxygen requirements aren't as high as large Orfe or Grass Carp.

 

[glolite]

Thanks for all your help. We'll keep testing the water parameters and hope fish are ok next summer. Might try putting the pump on for longer when it's hot.