Guide to growing koi fry from 6-8 weeks old

Hi there, today I will be showing you how I keep my 6-8 week koi and ensure they are kept happy and healthy. I purchased 100 6-8 week old mixed breed koi from an online seller called Newforestkoi koi. These were around 1" in length though many were much smaller initially. The picture on the right is of the koi when they first arrived. The water was in the bag fairly murky but this was due to the fact that they were kept in mud ponds in the retailers farm. Make sure you don't mix any of this water in with your tank/pond. Also bear in mind that these fish are very young and their immune systems are not fully developed so should thus be kept in near sterile water. They should not be kept with any other fish as they can easily spread disease or infections to these prone koi. If you do decide to risk them with other fish you should use a UV filter to eliminate most parasites.


I have been keeping these koi in a 150litre glass aquarium with 20% daily water changes. The filtration consists of :
1 eheim ecco external canister filter with sponge filter pads, clay media balls and alfa grog.
1 homemade internal filter. This filter works at about 3500 litres per hour and uses mainly ceramic balls, alfa grog, filter floss and carbon sponge pads. Picture below

And 1 homemade moving bed filter. This is power by an airstone and contains 1litre of K1 Kaldness filter media. This filter is very efficient at multiplying beneficial bacteria and keeps the water chemistry at a safe level. Picture below

Given the right nutrition and water quality these koi will grow extremely fast. It is important to feed them a varied diet at this age to ensure they are getting the right nutrition and vitamins. Avoid feeding them excessive protein. I feed these koi many different high quality sinking micro pellets, live/frozen daphnia, sinking bloodworm pellets, and brine-shrimp. If you have smaller koi you should feed them boiled egg yolk or brine shrimp or other smaller foods. Feed 3/4 times a day.
picture below of the koi 5 days later






































It is important to keep your water parameters in check. Ammonia and nitrite should read 0 on your test kits and you should keep your nitrate below 25 PPM. A UV filter would also be helpful as it would remove almost all potential parasites. Avoid over feeding as this will pollute the water. Siphon out any uneaten food, debris and waste daily so it does not rot. If you are using filter floss replace it every other day and clean any sponge filters when needed.

These koi are being kept in my cellar in a 150litre tank. A tank this size is too small to hold 100 koi for long this is why I am moving the larger koi to the outdoor pond when they reach a certain size threshold. Remember all koi are different, different genetics means different growth rates and coloration. I will update this blog as the koi grow to show their growth progress.

The first of the larger koi were added to the pond. These were around 3.5 inches long and settled in well. The larger koi initially showed a little aggression and chased them around but this later stopped. I added few fish every week or so during the last month. out of 80 fish in the pond 1 died to an unknown cause.

I would recommend you acclimate these koi for around 20+minutes especially if they were kept in sterile tanks.
It is also important to keep the pond parameters safe and consistent.

Close up

Another batch going in. The smallest koi was in there for comparison.

Another load going in

close up

close up

The cat was staring at the fish again :D

Feel free to ask any questions.
Thanks for reading I will try update the blog often :)

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