Aquascaping Answers: Surface Film and CO2 Safety

Each week in Aquascaping Answers, I do my best answering your aquascaping and aquascaping related questions. Just leave your question in the comments section!

Lots of good questions this week, so I'll jump right in:

I have seen a CO2 test by tetra in a LFS, I have also read its possible to measure CO2 with PH and hardness. What is the best and more accurate way of testing CO2?

You're right, you can get a general idea of CO2 levels from pH and KH (carbonate hardness). However this method is rough at best, since it assumes that there are no other acids or bases present in the aquarium. The most accurate way of testing CO2 levels that I have found is to use a drop checker. These are tiny glass or plastic tools that stick onto the aquarium wall and have a pocket of air separating a reagent from the aquarium water. The CO2 in the aquarium water travels through the air pocket and causes the reagent to change colors depending on the amount of CO2 present. These are generally fairly easy to make yourself, since the reagent is simply a fixed KH 4 and pH test solution mixed together, or you can buy a nice looking glass one for under $15. The only drawback of these is that they can be somewhat slow to react since the CO2 has to travel across the air pocket and into the reagent. But they are by far the most accurate method.

I have a 5lb CO2 tank. Do I need to take any safety precautions? I read the MHDS and it says that the space should be well ventilated. That is tough. What do you do? Would a carbon monoxide detector pick up CO2 before I suffocate?

If you can, I would follow the MHDS recommendations by all means. However, "well ventilated" can be a window or door to the outside. We all breathe out CO2 (and back in again) and it's present in the atmosphere, so unless your CO2 tank is in a small sealed area and your system is leaking drastically I don't think it should be too much of a problem (on a 0-4 scale it's listed as a "1 - Slight hazard"). The issue arises in a sealed or nearly sealed area where the CO2 levels can rise so far that it limits the amount of CO2 your body can get rid of. This is exactly the same thing that happens to fish when CO2 is too high. You would (like the fish) probably notice something was wrong (rapid breathing, headache). I don't think a carbon monoxide detector will detect CO2 though.

I think a more important safety measure is to make sure the tank is secure at all times with a chain or rope so it cannot tip over (causing liquid CO2 to enter the regulator and explosively decompress). This especially goes for transporting it. I've heard many stories of driving with a CO2 container not properly secured that hits something and opens the valve, instantly flooding the car with CO2. Or, even worse, if it falls over and hits something, breaking the valve off, it could become a very, very dangerous gas-propelled missile. Just be safe and realize you are dealing with a highly compressed gas in a pressurized container.

My 100ltr planted Cube has developed a surface film of algae, I tried the usual paper towel trick which does lift it but its back in an hour or so. I don't want to agitate the surface obviously but what else will work? I did introduce a new food recently so I'll stop that first. Any other suggestions?

This surface film is a build up of organic waste and proteins. I'd try reducing the amount of food you feed your fish if it's thick enough to bother you. Usually, it's just a slight film, but in bad cases it can get thick and may pose a risk to your fish since it can prevent gas exchange. The only way to get rid of it is to use a paper towel (like you've been doing) or to change your filtration so it agitates the water slightly (but not enough to waste all your CO2). One of the most effective tools to do this with is the ADA Lily Pipes. They are shaped to create a tiny vortex which sucks the surface scum off the surface. A similar effect can sometimes be achieved by placing a powerful outflow just beneath the surface far enough to eliminate ripples (or aimed slightly downwards to achieve the same thing). Good luck!

Ask a question about aquascaping, keeping aquatic plants, plant-friendly fish, lighting, CO2, fertilizing, or any other aquarium plant related question in the comments to this post, and I'll answer them in next week's edition.