what is problem likely to come if i change 50% water of my 400 lit pond in my garden having 20 fishes?

Answer 1

Changing that much water can stress the beneficial bacteria in your pond causing spikes in nitrites, nitrates and ammonia. If you are going to do so I would suggest not feeding the gold fish the day of and the day after such a water change. The reduced amount of fish poop will give the bacteria a chance to recover.
A

Answer 2

Not a problem.... Make sure the temp is within 5* either way of the pond before changing it. Even If it has gravel, you should do a yearly maintainence, spring and fall clean down with the fish removed. Mulm build up in gravel can be bad news and release toxic gas. Test the water in pond before, filters bio bugs use up the calcium and magnesium (gh & kh which controls your ph) as do the fish and any plants. A good alternating schedule of WC is good, I do 25% and every 4 weeks a 50, then alternate that 50% with a 75% through summer. Don't forget to add dechlor and if your on well water, spray it in, lots of splash, well water is notoriouse for being low on the oxygen if any.

With 20 fish in 400 litr, your also seriously overstocked, thats something like 25 gls.. Pond Goldies should have 50 gls each, and Koi, 250. You could be skating on thin ice sadly.

Answer 3

Jamie hit it all right on the head. Bacteria is not in the water, it's in the filter media and substrate. You should be fine changing that amount, especially with that many fish in a 100 US gallon pond. I've done it on my pond and on some of my tanks, when I've gotten off schedule. You'd be better off though doing smaller weekly water changes. Like he also said, make sure the temperature is the same. Cheers!!

Answer 4

Usually 20% is all that you should change. And only clean 1/3 of your gravel. Make sure you put water conditioner into the new water. But if you must change 50% the biggest problem would be disturbing the biological filter, therefore raising ammonia and nitrite. Add stresszyme to help it, and make sure the pH of the water in your pond, and the water that you are adding is the close to the same, or the pH change could kill your fish.

Answer 5

Go for it. There are only trace amounts of benifical bacteria actually suspended in the water, so go ahead and remove as much as you want as long as 1) the water you add is the same temperature as the water you took out 2) if you're on city water make sure to dechlorinate it, most wells are fine as is 3) don't let the fish or biological filtration dry out

Answer 6

I think it's ok. I have a tank with 5 fishs, each time I change water I only keep 1/4 old water, they still living well.

Answer 7

Never change water more than 1/3 of total amount...water creatures can feel the shock...

Answer 8

none as long as the water temp is about the same and you dechlorinate the water