My brother wants to have a spooky Halloween party. One decoration we debated was placing a chunk of dry ice in his outdoor waterfall pond. The dry ice will be going into top pond (around 100gal) then empties via a waterfall into a lager pond (around 1000 gal), for hopefully a misty cascading effect. The potential problem is: The lower, larger pond is well stocked with koi and regular goldfish.
Will the dry ice harm the fish? Will it make the water too cold or increase the CO2 levels too much? A recirculating pump keeps the water moving and the party will last around 4-5 hours.
The effect you’re going for will work much better in hot water.
I would be wary of the pH level in the pond, especially if you plan to have it smoking the whole time.
You could partially submerge a pail of warm water in the top pond (so the top sticks out just a little) and put the dry ice in there. Same effect, no mixing of water.
And the mist will just cascade to the lower pond and into the air on the surface of the water without mixing with it, right? I’m just trying to get a mental picture.
Dissolving CO[sub]2[/sub] in water is a frequently-used trick in chemistry to effect a large pH change. A typical trick is to put an indicator in the water that changes around pH 5, and the dry ice will gradually change the color of the solution.
The warm water suggestion is a good one, for two reasons: (1) it keeps the CO[sub]2[/sub]-saturated water separate from the pond, and (2) you want as much water vapor as you can to get the “misty” effect. The mist you see is just a low-flying cloud – the cold CO[sub]2[/sub] bubbles lower the temperature of the air below the dew point, and water vapor condenses. The warmer the water, the higher the dew point will be.
Changing the bucket of water a few times over the course of the party probably wouldn’t be too bad. You’re going to have to drop in pieces of dry ice every 5-10 minutes, anyway.
Yeah, I think that the carbonic acid will have the potential to harm the fish. Unless someone has some clinical trials that say that the koi will be fine, I would try the bucket suggestion mentioned.
The mist you see is water vapor, so that wouldn’t be too bad. If you were to use the separate bucket method, I would imagine the biggest danger to the fish would be the invisible, heavier-than-air CO2, which could sit on top of the lower pond. That shouldn’t be too bad if the pond is in a ventilated area.
If you drop large chunks of dry ice into a bucket of water, they will bubble like mad for a while, and then a coating of ice (water ice, that is) will build up around the dry ice, helping to insulate it. You’ll still get a little trickle of gas from it, but the major bubbling will stop. Either you have to keep adding small chunks regularly, or you need to break the big chunks up to get the ice off of them.
I would definitely put the dry ice in a bucket of water partially submerged in the upper pond, by the way. It wouldn’t be very good for the fish.
Another possibility is to go to a party supply store and rent a fog-maker. They’re not that expensive.
I dunno for sure, but as I understand it, it is simply water vapor. Again, as I understand it, the machine vibrates rapidly enough to take water and turn it into fog. Maybe someone with a better understanding of how it works will come along…
Most store-bought fog machines that I have seen come with some kind of liquid chemical that you add to the machine. They also have a smell to the fog. So it may be an ultrasound vibration, but it’s not just water thats getting “fogified”