Has anyone heard of this? If so whats the best way to release it?

that's definately one way of adding co2 to your space. Lots of users do it. Search for videoman40's threads on it.

as to the amount to use, i'm sure there's a tester to measure the co2 ppm in a room. without it, i don't know how you could accurately judge the concentration of co2 in a space if you just left a peice of dry ice to evaporate away.

first day with dry ice... Damn it meled fast.... hahaha.. think ill stick to water sugar and yeast..

it does go fast. a good way to keep it from doing so is put it in an ice chest and drill a hole in the side with a tube going out to your plants. That way it will stay colder and evaporate less quickly. It will give your plants a chance to absorb more of it. Took that one straight out of the book of videoman so he deserves the credit.

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It's the scale at the top right of my post(for newbies)

I use it regularly. The proper way would be to get a syrofoam ice chest, heat up a screwdriver, and place a hole through the styrofoam. Place the dryice into the cooler, with the top on, and as the co2 builds, it will escape through the hole you made.

You could even add a small hose to capture the co2 and carry it to your plants directly. Remember to keep it away from your light, as the heat will make it evaporate quicker.

The biggest problem I've found for growers, is to find it at a fair price. I pay $14.00 for a 50 lb block, and that is big.
If you need it, you can look for manufacturers and/or resellers here in your area.
Peace

still. i think its time to look at the bottle approach

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Abudsmokers_Journal

for a closet grow this bottle is 3+ weeks, you can even go down to a 5-10 pound bottle

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Abudsmokers_Journal

I use those too, they work pretty good, and for dry ice prices here..it's the more economical way too.

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It's the scale at the top right of my post(for newbies)

I have several tanks too, but in the summer.....heat is the enemy.
I do not use the method that I posted above, I use the dryice as a means of cooling my light, than I allow the co2 to fall from the light onto my plants.

I realize that using my method, the dryice evaporates even faster, but you cant beat the cooling effect of negative 89 degrees!

can you buy big blocks of dry ice in the uk?