Plants yellowing and dying + lots of fibrous algae


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Hi all,

Long-time lurker here, but can't solve my problem by reading any of the threads on here.

I've built a 25m3 pond for my in-laws last summer, it has a gravel filtration system. Which pulls the water from the planted zone, past the plants' roots to the deep (swimming) zone. It cycles the contents of the pond 2x a day. 2/3 of the pond is shallows, which are 20 - 40cm deep sand/gravel substrate, for plant growth. The shallows go down from the edge to a depth of max 60cm. I live in zone 7b and the water temp atm is 25 degrees celsius.

The pond was filled with well water and initially all was good. The water was crystal clear. After 2 months fibrous algae started to grow everywhere in the pond, but since there were few plants I reckoned we just have to be patient and wait for the plants to mature so they can soak up the nutrients. In winter all the plants were cut and the organic material removed, so not to add nutrients to the pond.

The pond is one year old now and contains approximately 200 plants of many different types. The plants have been struggling ever since they've been planted. Many plants exhibiting slow growth and many have yellowing leaves, some of which died. Last week even the water lettuce died. The only plants which are doing well are the water lilies, which are planted in a sealed basket filled with clay/gardensoil substrate and capped of with clay to hopefully stop the fertilizer in the garden soil from leaching into the pond. Fibrous algae have been growing in the pond since spring, but now in mid summer they are going rampant. The water is crystal clear, but there are fibrous algae everywhere.

There is lots of life in the pond, dragonfly larvae, tadpoles, snails, slugs and all kinds of amphibians I don't recognize. They all came by themselves.

I'm not sure what the cause of the algae is. I figured it's the fertilizer in the garden soil in which the lilies are planted, that leached into the water. I thought algae grow when there are too many nutrients in the pond. But since pretty much all the plants are struggling and dying this doesn't seem to be the case. My goal is to have a clear natural pond, without algae.

Could anyone provide any guidance or clues what might be the issue here?
 
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addy1

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Welcome to our forum!

It sounds like the plants are not getting enough fertilizer. But if the algae is growing that well, it is a indicator, like you said, or a lot of nutrients.

Can you post some pictures? I helps us "see" what you have and are talking about.
 
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Hi addy, this picture is from 2 months ago, late spring. After most of the algae were scooped/vacuumed out. I'll ask my in-laws for a recent picture with some closeups of the algae.

As you can see the water lilies, which are in baskets with substrate and fertilizer grow very well. The other plants which have been in the pool for 6-12 months, aren't really growing. Exception is watermint and some of the grasses.

We planted around 50 yellow water lillies ( Nuphar lutea ), directly into the substrate, initially they sprouted some leaves which reached the surface but quickly died down. After the winter they didn't come up, so I dug most of them up. All of them were (partially) rotting and some had tiny sprouts. I'm thinking many of the plants might not be growing well because of the substrate, allthough I read and have seen plants grow well in pebble/sand substrate.

Pond.jpg
 
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addy1

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That is nice! Love the planted area!

I would put in more plants, my bog you can't even see the pea gravel. It is nothing but plants. Test the water for nitrates etc, Some of those plants might be too low in the water. It looks like they are on the edge of the gravel, which might be shallow. Hard to really tell.

Without fish, the plants might struggle, they live off the fish waste. But you said there are other critters in the pond making waste products.
 

addy1

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And if you just planted it, pond plants take some time to get going good.

My pond cycles once every two hours or so. Is yours turning over just twice a day? You might need more flow.

I have a lot of lilies in my pond all fertilized with osmocote, the pond does not get algae, string, too many plants in the bog sucking out the nutrients for string algae to survive.
 
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Thanks for quick answers Addy! You might be right that some of the plants near the edge might have very shallow substrate, I'll take a look and move them if needed. I'll also measure my flow rate again and do the calculations, but I believe it cycles it just twice a day.

We try to keep adding plants, but at least 50% yellows and dies off within 1-3 months. The plants which are established aren't really expanding. I might just split and transplant the plants which do well, because I also think there should be more plants to out-compete the algae and make for a more resilient system.

I understand the plants don't do well when there aren't enough nutrients and I'd have no problem supplying them or adding fish and other critters, but since there are so many algae I'm hesitant to add nutrients because this might make matters worse.

So I'm still confused what could be the cause of the fibrous/string algae.
 
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addy1

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The plants on the edge most likely don't need more substrate unless it is really shallow. Some of the plants need to have their crown above water, some do fine with crown below water. That is more what I was referring to. My attitude is if the plant survives it is allowed to live.

Where are you at? I have water willow which grows great in water, gravel, bog, nice fibrous roots. Only about 12-18 inches tall with lilac flowers most of the summer.
 

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Hello and welcome!

Do you have any fish? Fish are the primary source of fertilizer for the plants, and the purpose of the plants is to use up that fertilizer.

As far as the water lilies go, they are great for providing shade, but since they are planted in their own containers, their roots don’t participate in reducing the nutrients.

Your pond looks awesome!
 
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@addy1 I live in Bratislava, Slovakia. Water willow looks beautiful, I should be able to find that here aswell. Thx for the tip.

@Mmathis thx, I hope it'll get even better when the plants really get going though. There is just one tiny fish in there since last week. I guess a frog or bird took it with them to the pond :D. I wanted to introduce fish eventually, but was hoping to stabilize the pond before that. I know the lillies don't help with the nutrients, but at least they look nice and grow well :D

It seems like you all agree there is a nutrient deficiency in the pond, meaning I'll need more/bigger critters like fish in my pond. But why would there be so many algae in my pond when the nutrient load is so low, the plants can't even grow? Seems like something isn't adding up.

I'm trying to understand the relationships here of what's going on.
 
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brokensword

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just wondering; have you added any salt to your pond? Salt isn't good for plants...you might check your well water and have it analyzed so you know what's in it. I have well water and the plants all do fine. Water lettuce usually does well, so I'm suspecting something is amiss with your water. Check on the pH, too.
 
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@brokensword no salt has been added, the ph is 6.8. I'm going to check have the pond water checked, which will at least tell me what the nutrient load is like. I just can't comprehend why plants are dying and algae are thriving. But like you said, there might be something in the water, which is holding the plants back..
 

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