Drawing outside air for gas exchange within your reef aquarium, whether this is through your skimmer or a “nano-bubbling” technique (I am in no way indorsing nano-bubbling, nor do I want to get into an argument about any potential benefits it may have. Enough said.) has increased in popularity due to the benefits of increased, and possibly more stable, pH values within our tanks. This can be especially effective when tanks are kept in basements or in modern, well-sealed houses. However, this practice poses an increased risk of contaminating your tank with unwanted particulates and chemicals, as many reefers can attest who have had all or part of their reefs killed by someone spraying a chemical close to the air intake. And these are only the acute effects of a significant dosage; it can be assumed that long term exposure of the reef to lower levels of contamination may also have negative effects.
This has been mentioned before, but I think a comprehensive overview of how to filter outside air that is going to be injected into the aquarium is in order. Most people have gone about this by duct taping a pre-made chemical canister filter made for respirators to their air intake. These filters are made of a particulate filter, activated carbon, and depending on the targeted chemical, a resin. However, these filters are expensive and they were designed for short term use in an application were size and weight are a concern. We can build a similar filter that will last longer and be cheaper to deploy using materials commonly available to hobbyist.
Particulate filter
Filtering air for particulates is very complicated, and actually hard to do effectively. Lucky for us the nice people at 3m have figured out how to filter particulates from air for us, so no need to reinvent the wheel. An N95 filter should work just fine, and will probably have less flow resistance than an n99 or n100.
Chemical filter
Activated carbon: AC does an excellent job of absorbing organic vapors, and depending on the type, will also do well with most inorganic vapors. AC is made by impregnating cabon with a decomposition catalysts. It is the decomposition catalysts used that determines the AC’s efficacy in filtering a specific chemical. Typical medical grade activated ccarbon uses a combination of molybdenum and triethylenediamine treatment, and is effective against a broad range of compounds. This is also what the higher grade AC sold in the aquarium trade uses, and what I would recommend if you don’t have access to medical grade AC (medical grade has the advantage of having a large variety of pore sizes). Other common types of AC employ silver, or oxides of iron and zinc. Sodium-, potassium- and alkali-treated carbon can also be used to absorb sewage vapors (hydrogen sulfide), chlorine, and other harmful gases. Any high grade activated carbon is going to do the job- so don’t sweat the type too much.
Other possible media: DI resin is made of divinyl benzene styrene copolymer beads, and can be used to filter air contaminates as well. However it is primarily used to remove molecular bases, including ammonia, organic amines, inides, aminoalcohols, alcoholoamines. So unless you have specific concerns, di resin can probably be left out.
How to build the filter
You will need:
2 PVC endcaps, in the next size up from your piping
Threaded to barb adapters in the size of your choice. I used ½’’ for the supply, and ¼’’ for the filtered side, as that is what my skimmer uses.
Vinyl tubing in your required length and diameter
A ~6’’ length of pvc pipe. 1.5’’ works well. I used clear acrylic because I have a bunch lying around
2 N95 disposable respirators
High quality activated carbon, the smaller the grain size the better.
Silicon sealant
Assembly
Drill the PVC endcaps for the barbed fittings. Insert fittings and seal with silicon.
Place 1 respirator over the end of your length of pipe. Insert into PVC endcap- friction should hold it together. Fill pipe with carbon, place 2nd respirator on the other end, and cap with 2nd PVC cap.
Attach tubing and start using.
How long this chemical filter last depends to a certain extent on the level of exposure to contaminants, but unless you live next to a chemical plant, the greatest variable is going to be humidity. I cannot really give a definitive answer on the useful lifetime, but because we are overbuilding these filters, they should work moderately well for an extended period of time. I would say once a year is a reasonable exchange schedule.
This has been mentioned before, but I think a comprehensive overview of how to filter outside air that is going to be injected into the aquarium is in order. Most people have gone about this by duct taping a pre-made chemical canister filter made for respirators to their air intake. These filters are made of a particulate filter, activated carbon, and depending on the targeted chemical, a resin. However, these filters are expensive and they were designed for short term use in an application were size and weight are a concern. We can build a similar filter that will last longer and be cheaper to deploy using materials commonly available to hobbyist.
Particulate filter
Filtering air for particulates is very complicated, and actually hard to do effectively. Lucky for us the nice people at 3m have figured out how to filter particulates from air for us, so no need to reinvent the wheel. An N95 filter should work just fine, and will probably have less flow resistance than an n99 or n100.
Chemical filter
Activated carbon: AC does an excellent job of absorbing organic vapors, and depending on the type, will also do well with most inorganic vapors. AC is made by impregnating cabon with a decomposition catalysts. It is the decomposition catalysts used that determines the AC’s efficacy in filtering a specific chemical. Typical medical grade activated ccarbon uses a combination of molybdenum and triethylenediamine treatment, and is effective against a broad range of compounds. This is also what the higher grade AC sold in the aquarium trade uses, and what I would recommend if you don’t have access to medical grade AC (medical grade has the advantage of having a large variety of pore sizes). Other common types of AC employ silver, or oxides of iron and zinc. Sodium-, potassium- and alkali-treated carbon can also be used to absorb sewage vapors (hydrogen sulfide), chlorine, and other harmful gases. Any high grade activated carbon is going to do the job- so don’t sweat the type too much.
Other possible media: DI resin is made of divinyl benzene styrene copolymer beads, and can be used to filter air contaminates as well. However it is primarily used to remove molecular bases, including ammonia, organic amines, inides, aminoalcohols, alcoholoamines. So unless you have specific concerns, di resin can probably be left out.
How to build the filter
You will need:
2 PVC endcaps, in the next size up from your piping
Threaded to barb adapters in the size of your choice. I used ½’’ for the supply, and ¼’’ for the filtered side, as that is what my skimmer uses.
Vinyl tubing in your required length and diameter
A ~6’’ length of pvc pipe. 1.5’’ works well. I used clear acrylic because I have a bunch lying around
2 N95 disposable respirators
High quality activated carbon, the smaller the grain size the better.
Silicon sealant
Assembly
Drill the PVC endcaps for the barbed fittings. Insert fittings and seal with silicon.
Place 1 respirator over the end of your length of pipe. Insert into PVC endcap- friction should hold it together. Fill pipe with carbon, place 2nd respirator on the other end, and cap with 2nd PVC cap.
Attach tubing and start using.
How long this chemical filter last depends to a certain extent on the level of exposure to contaminants, but unless you live next to a chemical plant, the greatest variable is going to be humidity. I cannot really give a definitive answer on the useful lifetime, but because we are overbuilding these filters, they should work moderately well for an extended period of time. I would say once a year is a reasonable exchange schedule.
