Growth problems

[Emanuele]

Hello,
it's since when i bought them that i noticed a very slow growth of my plants in the pond, in particular the floating ones. They became yellow and small, something weird for some invasive plants. I'm trying to fix the problem, due i thought it was luck of phosphorus, with a fertilizer of potassium phosphite with leaf application. After i diluited it (2ml on a litter of water), i used more or less 50ml of the new solution, following more or less the instruction on the bottle. But i think that fertilizer is specific for normal plants more than aquatic ones.

About the plants, the pistias stratiotes don't grow, they have a diameter of around 4 cm; the azolla caroliniana completely disappeared; the salvinia natas grow but it's not very green and flourishing; the same for the limnobium laevigatum. The other plants (mentha aquatica, caltha palustris, iris and pontederia cordata) grow pretty well even if i took off the ground from their vases to replace it with rocks, to make them get more nutriments from the water and make the water more transparent, but it is still green. The fishes don't go to eat the roots of the plants because some of them are in places not reachable for them.

Today i used the water test to have some values:
NO3- 0
NO2- 0
GH 8°d
KH between 6 and 10°d
pH 8.0
Cl 0
(some values could be not totaly right, due i used a test with the color comparition)

I ask help to anyone who have ideas to make my plants grow, thanks

Sorry for my bad english, i am not a native speaker so maybe i made mistakes

Here some pics of the pond:

 

[poconojoe]

Do you have any fish in there? My fish devour any Azolla or Salvinia. They eat them so fast, they don't have time to multiply. I try to save some in a floating net. They also eat the hanging roots of any floating plants.

We've had some discussions here about Water Lettuce and Water Hyacinths. I don't know if there was any final conclusions as to why they sometimes flourish and other times just don't grow. This year my Water Lettuce has literally taken over my pond, but for the last 3 years or so, they hardly grew at all. I personally, think there are different strains that fair well in different growing zones, but that's just a guess.

 

[Emanuele]

I have like 50 golden fishes and a lot of gambusias, i know that fishes loves the roots of floating plants so i putted some of them in a vase outside the pond (you can see it in the 3rd photo, the vase have bricks around), in that place the plants are safe. There is also a water bomb that bring the water in the vase (in the 1st photo there is a view from below of the vase) and then the water go back to the pond. I wanted to use the vase as a natural filter.

Anyway, the Azolla were in the vase, far from the fishes, so i think there is something wrong in the water, but i can't understand what and what to do

 

[poconojoe]

The only things I can think of are:
1. Not enough nutrients in the water to feed the plants. But you have fish, so the fish waste should provide enough nutrients.
2. Not enough sun or too much sun?
3. The Ph level is not compatible for the plants?
4. Temperature too high? I doubt this, but If the container is small with direct sun, the direct sun may raise the water temperature too high.

Hopefully others will chime in with some ideas.

On an unrelated note:
I'm just wondering why your water level is so low. Maybe you have a reason?
If you fill it up to the top, your fish will enjoy more habitat.

 

[Emanuele]

I will reply to your questions:
1. I think there are enough nutriments but maybe there is lack of an important one
2. The pond has a lot of sun to make the ninphea and its flower grow better. I tried to put the pistia in a place with less sun but without results
3. I don't know about the right pH for such plants but i think it's not so bad
4. Some of the pistia and salvinia are also inside the pond, where the water should be less hot but nothing changed

The water evaporated due the high temperature but soon i will fill the pond with rainy water

 

[AlyssaFish]

In my experience, too much sun is the killer of floating plants. The leaf turns yellow and the edges turn brown. Some species of plants will turn blueish or red when exposed to a high amount of sunlight. Azolla, for example, often turns red with brown tips.

I like to crowd my floating plants directly under sedge and cattails to give them protection against the sun. The ones growing in those areas are healthier than the ones in sunnier locations (although they're may grow more slowly, I'm not really sure).

It can take a plant a while to recover from too much sun. Often the old, yellowed leaves will not be suitable at gathering enough light in the new environment, and the plant will have to shed its old leaves overtime and grow new ones that are better suited to the current conditions. How long did you keep the water lettuce in a shady area before you decided it wasn't helping?

 

[Emanuele]

Between one month and two. I asked advices to the plant seller and he told me to give them more light. There are still some small pistia in the shadow part of the pond

 

[poconojoe]

Right now my pond is almost completely covered with water lettuce and water hyacinths. Mostly water lettuce. The only thing preventing complete coverage is the two air stones bubbling up to the surface.
Here's a picture:

 

[Emanuele]

Your ponds is so beautiful! And you are lucky, i would love to have Water Hyacinths but it is illegal in Europe

Anyway, i will keep using the fertilizer i talked about in the first message (i hope it's a good plan) and i will put the floating plants in a not sun exposed place for now. If someone have other advices, please, write here, i really want to make my plants grow in an healthy way

 

[cas]

If this is the first year for your pond and plants, it may be that the plants just need some time to mature. I added some new plants this year to my pond and they are yellow compared to the other existing plants.