Too Much floating plant?

[gsparsan]

I have a recently built 6000 L pond stocked with Koi, Goldfish and Iridescent sharks (all relocated from another smaller pond) and a few week ago I added some floating plants (water lettuce and giant duck weed). I have been away for 2 weeks and I received a picture from home showing that the floating plants have completely covered the pond in just those 2 weeks. The Nitrate levels are low but the pond receives direct sunlight for at least 6 hours a day.

My question is how does it affect the fish? My first reaction was that it has covered too much surface and will not be good for oxygen exchange into the water. So I have had 75% removed. Am I right in assuming this? Or on the contrary the plants are beneficial to the fish and I should leave them next time. Because I am sure there will be a next time if I don't do anything.

BEFORE:



AFTER 4 WEEKS

 

[dougall]

For the fish? You are right about the oxygen or gas exchange. If you had submerged plants(unlikely I know) it affects the light and nutrients they get.

You did the right thing, hopefully you composted the removed plants, as you see they overgrow quickly, so you really don't want them getting into local native waters.

 

[the loach]

It does not affect oxygen or gas exchange in your pond since you have a waterfall.
Don't worry, it is completely natural and harmless. The plants even prevent the water from becoming too hot for the fish and koi getting sun burn.
Oxygen level will be higher as without plants as the warmer the water gets, the less oxygen it contains.
With removing part of the plants you are making space for the plants to grow again and remove more nitrates.
It's like keeping up water quality by plant removal. Floating plants are important on tropical ponds.

 

[gsparsan]

Thanks guys. I am not worried about the plants getting into local waters because that's where the plants came from. I took them from the local river. But I will let them dry out before throwing into our green waste bin.

I think I will keep some 50% of the pond covered because now it's summer here and the fish can use the shade and cooler water. And I like the idea of removing nitrates from the water every time I remove plants and make room for more to grow. But I want 50% of the surface to be clear so that I can see the fish and use that to feed the fish etc.

In winter (tropical winter) we'll see if the rate of growth slows down.