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About CO2 Fertilization

Carbon Dioxide (CO2) is the most important plant nutrient. Almost half of the dry matter of any plant is carbon. In natural waters with luxurious plant growth a continuous flow of CO2 is supplied by CO2-rich nutrition springs and by fermentation processes in the ground. This natural CO2 supply is missing in the aquarium and an additional CO2 fertilization is essential. A deficiency in CO2 is the reason for unnaturally high pH-values and stunted or dissolving aquarium plants.

CO2 101 - Introduction to Carbon Dioxide

For plants to grow, they form carbohydrates (sugars) out of carbon dioxide (CO2) and water, using light as the energy source. This process is called photosynthesis.

In an aquarium fish and bacteria produce CO2 continuously. While plants use CO2 and have a net production of oxygen during the day, at night this process is reversed and they use oxygen and produce CO2.

In a well-planted aquarium the amount of CO2 that is produced naturally is relatively small and therefore the CO2 concentration is usually the most dominant factor limiting plant growth.

CO2 Equilibrium

CO2 gas dissolved in water can take the form of bicarbonate or carbonate. These three forms are in chemical equilibrium. Which form is present in what amount depends on the pH.

Dissolved CO2 <=> bicarbonate ion <=> carbonate ion

In the pH range favorable to water plants, pH 6.4-7.2, a percentage will be present as dissolved CO2 and the rest as bicarbonate ions.

From pH 8.0 to pH 8.8 there will be almost no dissolved CO2, a large amount of bicarbonate and a small amount of carbonate.

Although they are named "water plants", most aquarium plants are really swamp plants that grow in their natural habitat with at least part of their leaves above the water line. Therefore, they have adapted to take up gaseous CO2 from the atmosphere. In the aquarium, placed under water, they are only able to use dissolved CO2. Several real water plants, meaning species, which are always under water in their natural habitat, are capable of also using the bicarbonate ion if CO2 availability is limited. It is not however favorable to allow this to happen, firstly because many other plants in the aquarium will be unable to grow. Secondly, with the use of bicarbonate ions the pH will rise to unacceptable levels for all plants.

Because of the CO2 equilibrium discussed, the maximum amount of dissolved CO2 present is dependent on the pH. The lower the pH the more CO2 present.

Since plants use CO2 in considerable amounts, they increase the pH at the same time. Thus the pH value and the CO2 concentration are interrelated.

Carbonate harness (KH), is yet another factor that effects the concentration of CO2. Hard water, with a high KH can hold more CO2 than soft water. While it is essentially true that hard water with a low pH holds the largest amount of CO2 in practice we can only use the values most suitable for plants, which are pH 6.4-7.2 and 3-8o KH.

The water plant enthusiast faces the task of maintaining both a stable pH and hardness in order to establish an optimum CO2 concentration. CLICK on our "Test Kits" link for our CO2 Test Kit.

CO2 - Misc Components

CO2 - Non-Pressurized Systems

CO2 - Pressurized Systems

CO2 - Reactors


~We are mail order only & do not allow local pickups.  We only ship orders through UPS on Tues, Wed, & Thurs and we do not offer  weekend deliveries.

~ "Fish, Shrimp, & Snail Only" orders are shipped Tues night for Wed delivery pending availability.

~ "Plant Only" & "Live Animals w/Plants" orders are almost always delivered to you on Fridays pending availability.

~ We DO NOT sell sexed animals unless specified, please do not request paired or sexed fish.

~ Our minimum live good orders are $35.  There is NO minimum order amount for shipping dry good or non-perishable items.  You may combine Dry Goods and Live Goods to get to our $35.00 minimum.

~ YES, You may combine Fish, Shrimp & Snails with your Plant Orders and they are usually shipped in one box.

~ You must have your order placed by Monday night before we go home for same week delivery, agan, pending availability. Orders placed after our Monday deadline will ship the following week. 

~ You will get an email confirmation from UPS when your order ships out. 

All of this information is available in more detailed form by clicking the "Ordering" or "Shippng" tab above.  THANK YOU!









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CO2 tanks (or sometimes referred to as cylinders) don't usually come with CO2 systems, and usually cannot be shipped anyway. So, we recommend that you purchase your tank from your own local supply store and save big money on shipping and on the tank! Places like: Welding Supply Stores, Soda Bottlers or Vendors, and definitely Liquor Stores who sell Keg Beer will be able to accommodate your tank needs. There are many tank sizes out there but a 5lb cylinder is the most efficient. You should be able to find a good 5 or 10 Pound cylinder for about $50 bucks or less! Re-filling a tank should only cost from $12 to $15 depending on the store and should only need to be done 2 times a year at most. Ask your supplier for a used, or rebuilt tank for an even better price? Before calling anyone, be sure and measure the maximum height your tank can be so you can hide it under your tank in the stand.

Here's some good advice on getting a tank: It is possible that your state requires you to get your cylinder re-certified every few years to make sure it's still in good, safe, working operation. Many of today's cylinders are stamped with a date on them. Re-certifying a cylinder can sometimes be a hassle and cost you a few bucks and a few hours of precious time. If you don't get it re-certified you may be turned away to get your cylinder refilled. (Propane tanks are very similar) So, here's what we suggest; get your Co2 cylinder from a liquor store that sells keg beer. If they sell keg beer, then they certainly sell the equipment to operate a Co2-ran Kegmeister or beer tap. Check your yellow pages for a store close to home. If you go into your neighborhood liquor store and ask them for a 10-pound cylinder (see what other sizes they have available) for your Kegmeister, (if you tell them it's for an aquarium they might not understand) have it filled up, they won't ask you any questions and they will take a credit card number from you for the deposit on the cylinder. Typically a deposit is a cheap as $35 to $50 bucks. In 8 or 10 months when you go into the same store to have it filled again, they'll just charge you for the refill and that's it. Here's where this is a good idea.....one day that cylinder you got from that liquor store is going to expire and need to be re-certified. Well, when that happens, the employee will recognize that it is one of their cylinders, and just swap it out for a fresh one. Done! They won't charge you for a deposit on the new one, and everything is good. By then, they'll recognize you as a regular customer anyway. Your probably gonna end up buying chips, milk or beer from their store anyway. Everyone wins!

Lastly, with paintball wars becoming so popular, folks are needing to get CO2 cylinders refilled just to shoot their guns, so sporting goods stores are just starting to carry CO2 gas. This means it is only a matter of time before big box stores like Walmart carry CO2.