• You are viewing the forum as a Guest, please login (you can use your Facebook, Twitter, Google or Microsoft account to login) or register using this link: Log in or Sign Up

Little Shop of Horrors - How EI frightened the gardener


Expert/Global Moderator
11 Jul 2007
Almaty, Kazakhstan
I'm not really a pond person but I moved into a house with a pond of about 1000 US gallons and it was a mess. Green water, green slime and huge quantities of what appeared to be hair algae infested the pond. The gardener, who had been "taking care" of this pond for a few years had placed bales of hay in the pond. I guess there is some old wives tale about hay being an algecide. The pond had been unsightly for years and the plants, a small bullrush, a small lilly and a couple of other species which I can't identify were eeking out a meager living in this swamp. Algecides ahd been used in combat but clearly a new strategy was needed. I thought, what the heck, I'll ditch the hay bales and just start dosing EI and see what happens. When I informed the gardener he was agahst because everyone "knows" adding fertilizer to a pond encourages algae. After I offered a few choice words he left me to my own devices and I started dosing.

This is the pond one month after EI implementation began:

3 months after implementation the lilly flowered for the first time, ever.

4 months on the pond has become a Frankenstein. I still have a little bit of hair algae but it's a doddle to pull out. The lilly had completely covered the surface of the water and was growing out of the pond and onto the lawn. I had to prune severely. The bullrush is about 9 feet tall and the gardener refuses to go near it citing it's "unnatural" size and appearance.

I guess these are weeds in the corner but I'll leave them.

This is a closeup of the vigarous lilly growth. It's a jungle out there.


I suggested to the gardener that he should implement EI on the lawn because I felt it wasn't green enough. He felt I was suffereing from obsessive compulsive disorder (OCD).

Last edited:
How do you do IE in a pond? I cant see it feasable unless you change water in there. And the amount of ferts you would get through would be immense!

Incidentally the hay trick does work. Not any old hay but barley hay. Its good for clearing greenwater but wouldnt eally touch hair algae. Used it a few times in my dads pond.
Well it's easy, or at least I take the easy way out. Dosing is simple as you just have to calculate the water volume and ratio up from the standard EI dosing schemes. You don't have to add CO2 because the pond plants are more emersed growth than submersed so once the leaves break the surface they have all the CO2 they want from the atnmosphere.

You don't want to be changing water, and you don't have to. The water volumes are much higher so I figure the ammonia concentrations are lower unless there is a lot of leaf litter. If you remove leaf litter and dead insects/animals regularly with a scoop you can keep this in check. In this way it's more a combination of the low tech and high tech versions of EI.

A 1000 US Gal pond with plenty of biomass and a fair amount of sun would consume about 40 teaspoons of Potasium Nitrate per week but If you buy the agricultural 50 lb bags its really cheap. As an alternative you could also use the ferts sold for houseplants. A 2 Kg box of Miracle Grow will last about a month, and it's easy to dose because that size comes with 4 half kg sacks so I can dose 1 sack per week, more or less.
I've tried lots of different variations on theme. The trick is to be careful when using the commercial ferts that have urea or ammonia as their primary nitrogen source, but even these will work better than not dosing and using algecides which do nothing for your plants. I would be willing to bet it works better than barley hay.

It's really incredible because the pond community are even more terrified of NO3/PO4 than the unconverted aquarium community. I just recently browsed a shop which, on the shelf there was no less that five different brands of algecides yet there was not a fertilizer in sight. People cringe when I tell them what I'm doing but my water is crystalline and theirs is murky with marginal growth. I think some pond specialist shops sell magic formula bags for something like 60 quid per kilo. I'm pretty sure it's got the same ferts, but (shh) it's secret.

You're right that hair algae is really tough to eradicate in a pond without going over the top (I don't have that much energy) but I'm pulling out about a twentieth of what I was prior to adding ferts.

Well, yes, any of the terrestrial fertilizers can be used but I would only recommend their use in a pinch and then only on a well matured tank with lots of biomass. These are usually high in ammonia salts so you'd be playing with fire both from an algae standpoint as well as a toxicity standpoint. I used Scotts 14-7-14 for a long while when I was living in an area where I couldn't find NO3 and PO4.

If you have access to KNO3 and KH2PO4 there is no point using Miracle Grow.

No, these people are plugged into The Matrix and will fight to the death to preserve the system. Pond enthusiasts believe in the nutrient-causes-algae myth even more fervently than do aquarium keepers.

It's much more difficult in a pond because the lighting is unlimited and is uncontrolled but the same principles apply. I walked into a pond shop some time ago and couldn't believe how many algecidal products there were sitting on shelves. They occupied almost an entire aisle. Whatever space was not filled by an algae killer was occupied by test kits. Unbelievable. :shock: I do share my findings with pond owners that I know though and the response is amazing, clear water, minimal algae and beautiful flowers. 😀

Well, as long as you have high enough starting biomass, this is fine.
Once it's grown in however, you likely do not need to add so much ferts.

I'd go with more organic approaches at such scales, for small non CO2 planted aquariums, that's pretty much what you are doing, a similar approach should be applied here and for the lawn.........

I do organic composting + water wise irrigation because.....I live where it's hot and dry all summer and Fall.
No runoff gets into the storm drains, I chose plants that fit the climate and the location.

This ultimately reduces labor a great deal, and it looks good, I have far more diversity of insects and birds.
The same can be said for aquatic systems as well as the dry/moist landscapes.

Thus what reduces weeds in a crop field?
In your lawn?
In your pond?

If you add lots of Crops, lots of grass, lots floating lilies and grow them well and give then what they need...........it's actually pretty simple.

As far as the EI pond, use that water to to water the terrestrial plants.
I set up two large scale clients, one in southern LA with a huge 100metter x 6 metter deep bass fishing lake as a clear well for his palm growing operation. Another had a large koi pond, which the effluent was used for the landscaping with excellent results.

One of the goals is to develop a sustainable method, or at least as close as you can, that also saves $ and labor.
You can use Soil based planters, add at least 30-50% coverage on the pond in the early part of the year, generally Mar/Apr, then they will grow in and crowd out the algae.
If you add more ferts(Organic or otherwise), you will just get more weeds.

Consider adding some more fish to the system that are tough and eat the algae.
Flagfish ought to work and some shrimps etc, just make sure they do not get loose.

Raccoon's and birds are huge issues if the pond is less than 1 meter deep, shoot for 1.25 meters or deeper.
Also, make little platforms on the bottom to set the lily pots on.

The only thing they do the lakes and ponds I manage is really just plant harvesting and they use that for compost.
Generally about 1-2 month cycles during the growing season(9-10 months at leats here) they gob it out and add to the composter where it breaks down very rapidly. This can later be added to the lawn, trees, garden, other landscape plants etc.

If you are a farmer with a pond for watering your livestock, consider adding Azolla. Makes excellent feed when mixed with soy and other grains. then you can use that manure to fertilize the garden, crops etc.

This minimizes inputs in/out of the farm, yard, aquarium, pond etc.
While not a large issue for aquarist, it is far easier than any other methods and uses less energy.

However, for landowners/landscapes, agriculture etc, it makes a huge difference.
Not just the bottom line, but in the large scope of things.

You may need to add some K2SO4 to the ponds etc, or some PO4 here and there, but most of the N should be used via green manures,/compost. It's not hard and last years leftovers are this years ferts.

Tom Barr
Tom you suggest adding shrimp, I live in an area where the temperature gets down into the minus quiet regularly during winter what shrimp could I add that would be fine?
Garuf said:
Tom you suggest adding shrimp, I live in an area where the temperature gets down into the minus quiet regularly during winter what shrimp could I add that would be fine?

The restrictions for temperate invertebrates are very strict for a really good reason to protect our native species (though in some cases this is a 'shutting the stable door after the horse has bolted situation'). As we have no real native equivalent you should really forgo the shrimp IMO.
Hey Sam,
I'd like the City of London to try EI on their portion of the Thames. It's way too brown for my liking! New mayor in town though. I don't think he'd want to pay the fert bill. 😉

Shrimp are out, as are a number of algae eaters.
Likely could get away with Flag fish in the summer etc, even normal plecos.
However, I'd shy away from algae eaters in ponds.

There are some snails and mostly bugs that do this job pretty well, and the floating plants are very good as they do not get algae on the leaves anyway.

Still, better than a bale of rotting straw in your pond.

tom barr
Looks great!
Our ponds all have clear water, but you can't see it because of all the duckweed! :evil:

That lily in the second to last picture also looks like it needs splitting..
Ugh..duckweed can be brutal. The lily biomass removed was unreal. I split and re-split. It was easily 1/4 ton by the end of the season. As Tom pointed out I was way over the top with nutrient addition. I reckon if you get the lily going the pads will spread out and cover the duckweed.

Excaliber could do the trick🙂
A large knife, cut the sucker in 1/2, 1/4ers etc.
Choose where to cut to save the most leaves etc, the tuber root stock can get large.

You can sell these weeds also to the Lily clubs.
You can also make hybrid types as well.
Quite popular.

As you can see, you have very little algae and lots of weedy plant biomass.

Now take this a step farther, use the compost from the aquatic weeds to fertilize the yard, any landscape, garden near by.

Now, you can even forgo the KNO3 additions and switch to Azolla and add a little Chicken manure or PO4. Azolla is great for light blockage and it is easy scoop and add to gardens, and it's actually a better feed/grain amendment than soy beans(has a better amino acid content) for cattle, pigs, chickens etc.

Now you have gone all organic :!:
I am trying to work with an organic chicken company here in CA, quite large operation to raise and sell Azolla feed to them, and they in turn sell me Chicken manure. I can also sell the Azolla as green manure and a replacement for N fertilizers which have increased in cost and as a sustainable N fertilizer for organic operations.

Azolla doubles it's biomass in 2-3 days under lab conditions, 4-6 days under field conditions.
So adding a 500 gram wet weight ot a small pond should have it covered in a couple of three weeks or so.

Tom Barr