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Discussion Starter · #1 ·
So I built a new greenhouse last summer and decided it needed a pond. I picked up a 75g stock tank from a local farm store back in December, filled it with about 1.5" of topsoil from the woods in my backyard, capped it with 1-1.5" of gravel, planted it, and then filled it with water. Over the following weeks I added some Tetras and Oto's along with some floating plants.

Here it is 1 month after filling, still pretty cloudy.


By the second month the cloudy water had turned to green water. I added some willow cuttings, which are said to help clear green water. They grew quite well, but the algae was undeterred.


I finally broke down and added a 15w UV sterilizer. Within 5 days the green color had disappeared, but the water was still a very cloudy gray color. Over the following few weeks the water gradually cleared, but then hair algae reared its ugly head. It grew all over the tank walls and on some parts of the plants. I decided to dose the tank with hydrogen peroxide. Over the next few days the hair algae disappeared, which brings me to my current state, algae free!



I don't know how long it will last, but for the moment all is well. I'm hoping I can eventually remove the UV sterilizer, but I'm leaving it on for now. I'm guessing these algae problems stem from both the newness of the pond, and all the sun it gets. I've got it under 60% shade cloth now, and it should be shaded by taller greenhouse plants eventually.

A few tank specs:
76-82°F, 4 dKH, 4 dGH
2 Koralia Nano 425 powerheads, Maxijet 1200 to UV
No other filtration
Maybe 30? Tetras fed twice daily

Do you guys think I'm on the right track? Is there anything else I should be considering?
 

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You will probably always have green water without a uv. My pond did but then again mine was koi only. With the ammount of plants you have, it may be possible.
 

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Cool pond!

Did you ever check the nutrient levels of the water after set up? I expect the soil released a lot of nutrients after the initial set-up which induced the algae.

I recently set up my first tank w/ a soil sublayer and was amazed how many nutrients were released into the water column. I tested for NH3, NO3, PO4 routinely over the first few months (no light or heat or planting or fish -- just added the substrate and filled the tank) and the levels were very high. PO4 routinely above 5 ppm, NO3 >40-80 ppm, NH3 high (can't remember the numbers and don't have my notebook with me). I figured this would have definitely caused green water and/or other algae if I had it exposed to light and not changed the water regularly.

I changed large portions of the water until the levels dropped and then set it up.

Good luck!

-Roy
 

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Discussion Starter · #4 ·
Thanks guys.

I have never found any nitrates in my tank, although my test kit is expired. I should get a new one. The plants/algae may have been sucking up nitrogen compounds as quickly as they were added though. The pond has definitely settled down after 3 months. Water is finally clear and I haven't lost any fish in quite a while. My silver tip tetras actually reproduced, and the little guys are starting to get quite big. The Hygrophila, Heteranthera, and Rotala have grown a ton, and the more recently added Mayaca is coming along as well. Vallisneria is alive, but looks pathetic. I'm guessing my water is too soft for this plant. I also have floating Frogbit and Salvinia (which I removed for the pictures) that have to be thinned regularly. I just toss them on the raised bed in the greenhouse, which is nice.

I'm just waiting to see if the algae stays away now, and whether I'll be able to ditch my UV. Maybe I should just be brave and shut it off. It should be easy enough to kill if it comes back.
 
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