Walstad Goldfish Tank Update October 2009
September was an interesting month for my Walstad tank. For the second time I went away on holidays and then when I got back had problems that needed to be addressed.
The last time I was away I came back and Tiger had a white patch of fuzz on her and died shortly afterwards. This time when I came back I was greeted with a lovely tank full of green algae water.
I decided this would be a great opportunity to do some replanting and re-arranging inside the tank.
First I got rid of the amazon sword in the tank and replaced it with my largest crypt. Even in a 4ft tank the sword was simply just too big and whilst the crypt was almost as large, grows much more compact then the sword which liked to spread out and completely take over the center foreground.
I also thinned out the other crypts which due to their size were crowding eachother out. I was very happy with the corkscrew vallisneria at the rear right so I pulled out the plants I had growing on the rear left and after dividing up the vallisneria I had, spread it out on either side.
Corkscrew vallisneria grows quite densely and after seeing what happens when the plants take off and how much room they can potentially take up I’d rather have thin plants then the bushy ones so that the fish have more room to swim.
I also rearranged some of the java ferns on the driftwood centerpiece and spread them out a bit, they’ve got a much better shot at completely covering it now. After doing all this and despite a 100% water change, within days the green water came back as strong as ever.
At this point I’m not sure what was causing it. As far as I could tell green water happened when there was excess nutrients or a nutrient imbalance, which made no sense seeing as nobody fed the fish while I was away. I’d have thought a Walstad tank setup for 5-6 months would be capable of producing enough ammonia on its own to keep the plants going for 5 days, apparently not.
When I rearranged the tank and refilled it I’m also not sure as to what brought the green water back so quickly.
In any case I decided that another water change wasn’t going to do much so I started a course of treatment known as the ‘blackout method’. I’ll write a more detailed article on it in the future but the gist of it is you completely cover the tank for a few days and this light starvation clears the water.
When I completed the treatment the water was still a bit cloudy, but looking much better.
That was about a week ago now and I’ve watched the water seems to be slowly heading back to green again. I’ve since also thinned out the floating hornwort I’ve got in there to promote new growth and compete with the water algae. Here’s what it looks like this morning:
This time I’d probably leave it for a month and see if whatever the green alagae water is feasting on runs out (it can’t all be ammonia as I’m getting plant growth and no new algae growth on the glass or plants). Replacing the water seems to have hurt the hornwort somewhat in that it’s gone yellow while it adapts to the new water.
At this stage I’d love to experiment some more with the walstad method and goldfish but my time is running out. I plan to move overseas by the end of November and sadly I think at this stage I’m going to be surrendering the goldfish to an aquarium and tearing down the tank.
I didn’t have any green algae water problems with a canister filter running in the tank but I have a feeling the cannister filter starved the plants somewhat and was counter productive to having soil in there which is supposed to do the filtering job. What I’d like to see is if a small internal filter placed near the top of the water so as to trap as little as possible of the mulm on the gravel, would have any effect.
I’m most likely just going to leave the tank now until I’m ready to leave and see if the water clears up on its own and how the plants react, just as an experiment so if I ever get back into it at a later stage I know whether waiting or not is going to achieve anything.
While I’m overseas I might set up a tank once I’ve got my accommodation somewhat stable but it won’t be anywhere near as big as the tank I’ve got now. I’d also probably stock it with tropical fish seeing as without further investigation I’m not entirely sure a 100% filterless Walstad tank with goldfish is possible to maintain.
The good news is my tank is going into storage here so when I do make my way back I can always get back into it. Unless anything amazing happens over the next month and a half this will most likely be my last entry into my Walstad tank journal for a while.
Thanks for reading and hopefully my experiences help anyone else out there who’s willing to try the Walstad method with goldfish in the future.
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