I want to grow algae, not mosquitoes.
June 16, 2017 3:07 AM   Subscribe

I am an artist and I'm working on an interactive installation piece that involves a sculpture submerged in still water in a vase in order to grow algae on it. I have been growing the algae well for a week or so now, but today for the first time I noticed mosquito larvae in the vase. How do I kill the larvae and not the algae?

I did some googling and as a possibly temporary solution I poured vegetable oil on top of the water. From the googling, though, algae can be negatively affected by oil, too, and the oil can also go rancid (though educated opinions about this are welcome - especially regarding how long I have before the oil itself becomes a real problem). This is a vase holding less than two liters of water; would a small part of one of those floating mosquito donuts work? A lot of the google results are either for much larger quantities of water like ponds (get some fish!) or for water that does not need to hold living plants (lots of chlorine! the oil! drain it and refill it!).

I ideally do not want to have to figure out how to get this water constantly flowing (ie attempt to add a small fountain thing to it). I would strongly prefer something akin to the oil or donut solution. Also, I am currently abroad in Madrid, shipping is a bit of a tricky issue, and I can't easily buy anything really hard-to-find; I imagine I'll need to be able to acquire this in a standard bazaar. I don't even know for sure yet if they sell mosquito donuts, but I imagine/hope I can find one.

My primary goals are: 1) encourage algae growth; 2) discourage mosquito growth; 3) not cloud the water so much that seeing the algae/sculpture is impossible; 4) other aesthetics like visuals/smell.

I will have an exhibition of this piece on July 20-28, and plan to grow the algae on the sculpture until then. I also plan to do this with a second, bigger sculpture and bowl/aquarium of water holding perhaps 10 liters of water.
posted by vegartanipla to Home & Garden (8 answers total) 1 user marked this as a favorite
I've had success with a similar problem by putting bits of copper wire in the water, which apparently prevent the mosquito larvae from developing. Just take a short length of normal, household electrical wiring of the braided type with several narrow-guage wires, and strip off the insulaton. Since it's an artistic installation and you presumably don't want something ugly to be too visible, you can wind the copper wiring into spirals or whatever and hide them somewhere.
posted by aqsakal at 3:22 AM on June 16, 2017 [1 favorite]

Two litres is far less than you need for fish, even tiny ones. I'd also hesitate to suggest keeping fish in an environment where you're not providing proper conditions, like clean, filtered water. So let's rule that out.

Can you do regular water changes? The larvae will be removed (for the most part) if you do this. And anyway, you probably don't want the sort of algae that will cloud the water. so water changes are a good bet. Most aquarium keepers (including me) struggle to prevent algae from growing, which it will still do even in the cleanest water. All you need to do to encourage algae is expose the water to sunlight, and maybe introduce a few nitrates (a few drops of liquid plant fertiliser ought to be ample).

Keeping the vessel covered with some cloth and a rubber band will prevent further ingress by mosquitoes.

Mosquitoes don't like moving water. A small aquarium pump and some air line will create enough water movement to make the environment much less attractive.

Presumably the above things are possible while you prepare your piece. When it's on show, do you have the option of covering/aerating/changing the water when it's not on show? Or are you going to have to leave it unattended for days at a time?
posted by pipeski at 3:26 AM on June 16, 2017 [3 favorites]

Yes a small bit of a mosquito dunk will work. I've also used a goldfish in a similar situation - I did feel a bit bad about the aeration in a small volume but my surface area was pretty big.

After you get rid of the current larva/a why not just screen the top of the vase to keep future mosquitos out?
posted by sciencegeek at 4:27 AM on June 16, 2017 [2 favorites]

Have you considered just covering the top of the vase to prevent insect access (or escape)?

The mosquito dunks will work. I strongly recommend putting whatever small bit you use inside a fine mesh bag, since the material (of the ones I know, anyway) will break apart into little wood particles after a while.
posted by amtho at 4:36 AM on June 16, 2017

I would do a change of water and then make sure the vase is covered, maybe with a cheesecloth and rubberband to prevent further infestation.
posted by amanda at 4:42 AM on June 16, 2017 [2 favorites]

Any product containing BT will work like a charm, including mosquito dunks. It's a live bacterium that kills certain insect larvae but nothing else.
posted by Rust Moranis at 5:20 AM on June 16, 2017

Response by poster: OK, so far no store in Madrid has even heard of mosquito dunks, let alone sells them. I do have one other lead, though, in a store that's closed until later this afternoon so I'll check on that then.

Unfortunately copper also kills algae, or I'd do that - I hadn't considered it before though and it's a neat trick. And I have no idea why I didn't think to cover it with cloth from the beginning, but I definitely will do that, so if necessary, I'll change the water and then do that and then hopefully not have to mess with it again because I do actually want as much algae as possible (even the cloudy algae!). (And sorry if I was unclear - my mentioning fish was basically to point out that it wasn't a possible solution for me.)
posted by vegartanipla at 6:25 AM on June 16, 2017

I feel like you are reinventing a wheel? What you're describing is a fish tank. You should consult with an aquarium hobby group. There are many kinds of algae, with different needs. You're an artist, think constructively instead of destructively. Instead of killing the larvae, either prevent or leverage it. Don't fight, the lazy way is the best way. You can solve this problem with a twelve cent goldfish.

>figure out how to get this water constantly flowing

Any aquarium pump will do this, air or water.
posted by Area Control at 12:02 PM on June 17, 2017

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