Suppose you have a steady supply of dry ice arriving with orders at your place of work. Would it be possible/safe to make a storage tank for a little dry ice that, after sublimation, could then be infused into the aquarium at a constant level? If a cup of sugar powers the yeast DIY system, I'm sure a cup of dry ice will provide 10x more CO2. I just can't think of a way to do it that doesn't involve me wearing a flack jacket and a helmet every time I feed the fish

Any ideas for the technically challenged?

funny, I was just thinking about this today. . . your biggest problem would be in controlling the rate of sublimation and thus the rate of adding co2. I think the cost for developing a system that can do this would outweigh the cost of pressurised. But hey if you like the tinkering aspect go for it. Just start with really small amounts.

Ha, I'm always looking for a cheaper way out. What if you just use the lump of dry ice to pressurize a larger tank? The problem is finding the tanks that would do the trick and being able to guess their pressure limits! I don't know if there are check and pressure relief valves for low end pressures. Maybe just an inflatable device. I think I'm still a little leary I'd blow somethin up.

A true Gas Geek project.

Someone on the rec.aquaria.freshwater.plants newsgroup was tinkering with this a couple of years ago. A GoogleGroups search might come up with the thread.

If I remember correctly his solution was to machine a pressure vessel which could be unscrewed to recharge it with dry ice. I don't remember if the project went very far; it could have been that either I stopped reading the newsgroups about that time or he suddenly stopped posting.

If you could lay hands on a 3000 p.s.i. filtration canister with a big screw-off o-ring sealed end and the associated high pressure check valves and regulator I don't see why you couldn't cobble something workable and relatively safe together. Considering though that I just had a handful of similar components arrive on my lab bench today along with a bill for $300 you won't save money if you have to start buying the parts.

They sure are shiny though.

Well, if you put the dry ice into a pressurized container, then you're kinda losing the safety, simplicity and economy of a non-pressurized system, yes?

Someone told me the way dry ice is made is with a special fixture that attaches to a large CO2 tank. When you release gas under pressure, it gets very cold, and the fixture uses that to freeze a portion of the CO2. But a lot of the CO2 is wasted, so it would serve to reason that dry is ice more expensive than plain CO2 per pound.

Of course, if you're getting it for free and no one cares, go for it.

The diagram looks like it could work. I'd use an old compressor tank as the gas storage tank - then at least you would know the pressure rating. Just remove the motor, add a screw-on plug and drop the CO2 through that hole. If you put in a pressure relief valve, you'd have a fairly safe system.

Kevin

You could use soda kegs - not sure but think they are rated up to 125 psi.

They make them in several sizes, but 5 gallon is cheepest I think, the little ones get pricy.

My question would be how much pressure drop would you get daily from a 5 gallon resevour of co2.
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you could effective lower the gas volume of the tank by adding water. If you used 2 tanks - one could have a small gas volume and be used as a generator tank.
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I bought mine used a long time ago, in 1990 they were about $10 each, no clue today.

Thanks for the feedback and sugestions! I'll have to see what kind of parts I can find and whether or not it will be more trouble than it's worth. I may have to dig out my old chemistry book and see if I can calculate the volume of gas to expect based on the weight. I'm sure I'll be needing it to understand the water parameter forum. Hopefully you'll hear from me again

I think that if you could tinker with an insulated container, you could find the ambient tempurature that causes sublimation in the dry ice at just the amount you need. A problem that might need to be overcome is that you would need to purge the various tanks, regulators and lines etc. of air with each dry ice change.

*edit* This sort of system might work as a low pressure system, like DIY yeast/sugar.

I'll save you the trouble of the chemistry book.

1 lb. dry ice = 8.62 cubic feet of CO2 gas

If you really want some killer CO2 info and methods, look up info on... erm... cough... hydroponics, yeah, that's the ticket. The marij... erm, hydroponics people got it all figured out.

Man, that is the mother load of CO2 info...had me feeling a little short of breath after reading it It was interesting to see that the costs for the dry ice and fermentation methods are the same.

I think just using the natural sublimation rate would require a lot of dry ice, even if it was in an insulated container. I was hoping to capture all of the gas for controlled infusion, but it may be a lot harder than I thought. I think I'll just keep an eye out for suitable equipment. The soda kegs sound like the best bet so far if a pressure valve can be inserted.

Thanks again!

Maybe for the application the website is describing, but it doesn't translate to our application. They are talking about using a pounds of sugar, while we use much less. It just doesn't translate. equating the two in our application is misleading.

Hydroponics? No need to cough or clear your throat. It has been mentioned here a quite a bit. No need to make allusions to drugs either. It was developed as a method to grow food crop.

Mike

How so? One pound of sugar is theoretically capable of producing so many cubic feet of CO2. One ounce can theoretically produce 1/16th as much.

I re-read the document at the link I provided. Seems I was mistaken.

The document I *was* looking at a few nights ago when researching alternate forms of CO2 production had some additional information, such as "risks of regularly transporting dry ice to the growroom", and "burning hydrocarbons may help eliminate unwanted smells", and was obviously targetted at drug farmers. I didn't save the link, so when posting it here I attempted to relocate the document by repeating the search terms I originally used in Google from memory. This document is almost, but not quite, the same.

Before the drug crop industry was injecting CO2 into their grow rooms, the general hydroponics industry (which WAS developed WAY before it became the 'in' thing to do to grow drugs) was already doing this. You can do a google search and find plenty of white papers done by various government institutions and colleges (including NASA) on how to do it. I get really annoyed by people who think that all hydroponics is for is to grow drug crops.

Myself, I have grown hydroponic tomatos, herbs (like chives, parsley, rosemary, etc) and chile peppers in a growroom using some of http://www.genhydro.com/ modules, along with some flourecent lighting for vegetative growth and a 400w HPS lamp for flowering growth. I also buy food at the local farmers market from companies who specialize in large greenhouses for hydroponics so that they can offer fresh, organic vegetables in the Colorado area, especially during the wintertime.

Heck, NASA has been growing hydroponic plants for years in their space stations, and uses the General Hydroponics line of fertilizers. In fact it is a key part of getting people to Mars.

Are there things that can be learned from hydroponic growth that can be applied to planted tanks? I would say so, yes. EI made complete sense to me after dosing with the FloraBase line from General Hydroponics, which uses the same kind of estimative methods. It also uses an estimative dosing schedule, based on the grower paying attention to the health of their plants. It works really well. CO2 injection made complete sense to me because I had read about it and seen other greenhouses do it that produce veggies on a mass scale, but I had never tried it myself at home.

Anyway, enough lecturing.

Robert

Sorry, I certainly didn't mean to suggest that.

As I stated, the link I *thought* I was providing was targetted to drug farmers. If I remember correctly, it also included one additional option which isn't in the link I *actually* posted - spending time in the grow room and providing CO2 via your own respiration. This concept is also detailed in TheKrib's website for aquarium application. Fill a garbage bag with your breath, bubble the contents through an airstone.

The most efficient means of CO2 supplementation in terms of controllability and cost of consumables is pressurized. Period, end of story. However, some people prefer to seek alternatives due to other factors. Those factors will vary depending on whether you're an aquarist, a legit hydroponics farmer, a drug farmer, or an astronaut growing veggies in space. To sample the full range of creativity in the art of supplementation, the drug-farming information should not be ignored, regardless of our dislike for the final application.