The beauty of our hobby is that there will always be a calling to take up just one more challenge. You know how it goes, at 5 years old we might get that gold fish in a bowl, then along comes the 10 gallon tank of tropical fish, a bigger tank to house all those free guppies, the monster tank in the bedroom room and so it goes on. Money of course is no obstacle! Then one day you think to yourself, wouldn't it be nice to have one of those DUTCH tanks in the middle of the living room. You know. the type filled with healthy looking plants, and aqua-scaped to look like a million bucks. Unfortunately, after a few enquiries on all that special equipment and additives that drives such a master piece, you will realise that it comes at an astronomical price tag. Well the good news is that you can have your cake and eat it, but you do have to take up a few DIY (Do It Yourself) challenges along the way. For one thing, you will need to develop some basic understanding of biological and chemical processes. Another is to think creatively so that you can develop the required gadgets and methods, as well as zero in on various readily available cheap chemicals that are going to help foster a good plant environment.

 

 

It is not for me to deprive you good readers from the above challenges, cause that would be like really mean. Wouldn’t it?

 

But....... the end of this article is not yet in sight, since the title implies some 'talk' about CO2 in the aquarium. Besides, I do actually feel like writing something more substantial.

 

 

One of the key elements of a Dutch tank is the infusion of CO2 into the water for an improved plant environment. Healthy plants actively conduct the process of photosynthesis in the presence of adequate amounts of light, heat and CO2 (water is also needed and should be plentiful in an aquarium). Photosynthesis produces a type of sugar (hexose) and liberates oxygen. Sugar in turn is the energy source used by the plant to metabolise various nutrients for growth. It goes without saying that if we do not provide enough CO2 then the plants have limited growth potential. Also worth mentioning at this point is that plants will do anything to get CO2, even by extracting it from the carbonate hardness agents that are dissolved in water (more about this later).

 

 

Properly infused CO2 will dissolve into the aquarium water (H2O), and a small amount of this dissolved CO2 will react with water to form Carbonic Acid (H2CO3).

 

The formula for this reaction is: CO2 + H2O = H2CO3.

 

In turn a small amount of the carbonic acid will dissociate (split apart) into its ionic components, a proton (H+) and a bicarbonate (HCO3-). The increase of protons (hydrogen ions) in water causes the pH of the water to drop (ie makes it more acidic). That's not the end though because a small amount of the bicarbonate ions also dissociate to result in yet another proton and a carbonate ion (CO3--). Once again the increase in protons affect a pH drop, and thus the bicarbonate ion behaves as an acid. If we remove any CO2 then the amount of bicarbonates and carbonic acid must also reduce, this reverses the dissociations that took place and hence the pH of the water increases. Since photosynthesis removes CO2 from water it is clear from the above discussion that the pH of the water has a tendency to rise during day-time (photo-period). Infusing CO2 into the water at the same rate as its removal by photosynthesis means no change in pH, and that is good for plants and fish.

 

The relationships that dictates the extent of carbonic acid formation that takes place is complex and involves the carbonate buffering system (future article if there is interest in this). For now it suffices to say that the amount of dissolved CO2 is related to the carbonate hardness (KH) and the pH of the water. Carbonate hardness is simply a measure of the alkalinity of water, and alkalinity is simply the ability to neutralise acids. Various aquarium books (eg the optimum aquarium) provide tables that allow you to determine the amount of dissolved CO2 based on the pH and carbonate hardness of the water. If you are any good at mathematics then you can use this formula to calculate the amount of dissolved CO2.

 

Carbon dioxide in parts per million (PPM) is:

 

CO2 = KH (1 – 10^(7-pH)).

 

 

Without CO2 infusion there is a real possibility that plants will deplete all of the dissolved CO2 in the aquarium water during the photo-period. When this happens some plants will extract its carbon needs from dissolved bicarbonates. This reaction is called biogenic decalcification and effectively breaks down (removes) the bicarbonates dissolved in the aquarium water. Since bicarbonates are acids (see above) then its removal causes an increase in pH of the aquarium water. The bicarbonates that are involved in this process must come from a bicarbonate salt, since there is no free CO2 and hence no carbonic acid to dissociate in a bicarbonate (got that). The bicarbonate salt is mostly calcium bicarbonate Ca (HCO3)2, the agent that makes water hard (temporary hardness).

 

The formula for biogenic decalcification is: Ca(HCO3)2 =CaO3 + CO2 + H2O.

 

Since calcium carbonate (CaCO3) is insoluble, it can be seen from the above formula that biogenic decalcification results in a calcium carbonate precipitate (white stuff on the plants). The C02 produced is of course used to satisfy the biological needs of the plants as described above (and we get some extra water too).

 

If you're happy with the above explanations then do not read the following paragraph, instead skip right to the next section viz, 'DIY Carbon Dioxide System'.

 

 

If you have turned to this paragraph then you must be a sucker for punishment, or you have been saying to yourself "this chap tells crap". Crap because everyone knows that to increase the pH of the water you add a bicarbonate salt (eg baking soda), so removing a bicarbonate salt should decrease the pH.

 

Well, you're right............... and so am I. This is because a bicarbonate is an amphiprotic substance ie, it can behave either as an acid or a base. Which way it behaves depends on whether it needs to react with an acid or a base. If you want to increase the pH with a bicarbonate, it must mean the aquarium water has an excess acid component (usually carbonic acid). In this circumstance the bicarbonate acts like a base. In the situation of biogenic decalcification there are no carbonic acids left and the pH is already quite high. Hence in this circumstance the bicarbonate acts like an acid.

 

Want more on this caper..................................... DIY.

 

A very easy way to infuse CO2 into water is by bringing it into contact with the water over a fixedsurface. A 40 gallon aquarium with a water KH of approximately 4 degrees (70 PPM ) is satisfied with 20 to 30 cm² Of CO2 surface. You can use upside down jam jars or tall drinking glasses to create a C02 gas bell that lasts a few hours. An aesthetically more pleasing gas bell can be made from pieces of window glass siliconed together.

 

 

Make a bell jar about 15 cm deep, 20 cm long and 1. 5 cm wide (the C02 in this will last for up to 1 0 hours, and is perfect for one photo period). For larger aquariums, or if the KH of the water is higher, the mouth of the bell needs to be increased as per table below (surface area required is not that exacting).

 

............... Carbonate Hardness (KH) in German Degrees.

 

Various methods to obtain C02 are described in aquarium books. However none of these appeal to me as they are either to messy, to bulky, to costly, or just a proverbial pain in the butt. As a DIY person I was always on the look out for the perfect C02 solution. One day (many years ago) I struck it rich when my attention crossed over to those soda stream Fizzy Drink Makers (FDM). Surely I thought, this contraption is the answer to my prayers. And just to confirm its potential I proceeded to pull one apart, right there in the shop (after all I was going to buy it, maybe).

 

Fig 1. and Fig 2. shows what the FDM looks like.

 

 

The soda stream FDM uses a 250 gram (net) CO2 gas bottle. This gives you a whopping 125 liters Of C02 gas, enough bell jar refills to last at least 6 months (even if you are a bit sloppy). CO2 bottles can be exchanged for recharged units at Kmart or Big W for about $6.00. Second hand soda stream FDM (complete with an empty gas bottle) are regularly available at Cash Converters for between $10 to $25.

 

To make a fizzy drink. First, the glass lemonade bottle (3/4 filled with water) is pressed against a rubber seal by pulling the handle on the FDM forward. Second, a firm press on the FDM carbonating button charges the lemonade bottle with CO2 (the fizz in the drink). If you over charge the lemonade bottle a pressure relief valve operates to discharge the excess gas pressure (this prevents the lemonade bottle from blowing up). The pressure relief valve is connected by means of a clear plastic tube that runs along side the CO2 gas bottle.

 

This plastic tube provides the means to tap into the mechanics of the FDM for our horticulturally ulterior purpose.

 

 

Purchase a soda stream FDM (you need to do this). Cut a 6 mm hole in the back cover on the side where the plastic tube is situated. Cut the plastic tube at the height where you have drilled the hole and fit in a plastic T piece. Suitable plastic T pieces are the typewith barbed ends (eg the kind used for micro irrigation systems) and are available at any plant nursery or Kmart. Slip on a piece aquarium air hose onto the remaining free end of the T piece. Secure all of the T piece hose connections with plastic cable ties (of course you get those at Kmart's automotive section), Finally, slip the air hose through the hole in the back cover and put the cover back on the FDM.

 

Having converted the soda stream FDM and constructed a bell jar I can assure you the worst is over (truly). All that is really left is to hook the air hose from the FDM to the bell jar via a check valve and purging tap. Fig 3. shows the complete DIY C02 system in schematic form. Take note of the way things are placed.

 

 

 

What can I say, get the bits and connect everything up as per Fig3. Also, secure the bell jar in the aquarium with its mouth below the water line (be inventive, use double sided suction caps). Don't forget to bring the CO2 feeder hose all the way up to the top of the bell jar (so you can purge it). And, lock an emptylemonade bottle in the FDM.

 

Important Note: CO2 will draw water up the feeder hose when the bell jar is empty (filled with water). To prevent back siphoning water into the FDM a reliable check valve needs to be fitted in line with the feeder hose. I recommend you use the type with the spring loaded neoprene (black rubber) insert. Other types may not close completely with little back pressure, or tend to disintegrate over time.

 

 

Every morning give the carbonating button a little push to fill up the bell jar. Over time some air will get in the bell jar and this progressively reduces its C02 holding capacity. When the bell has too much air in it, just let it escape by opening the purging tap (clamp on hose).

 

CO2 is not the end all and be all of plant growth, other factors are also very important including,

 

  1)  quality and intensity of lighting (don't buy expensive 'aquarium' fluorescence tubes,

  2)  availability of nutrients (major, minor and trace elements),

  3)  proper substrate mechanics (more DIY),

  4)  fish population, and fish foods used.

  5)  water quality (total dissolved solids, hardness, redox potential)

  6)  and more.

 

However, most hobbyist get some improved plant growth with CO2 infusion. Some get quite a dramatic increases in plant growth, despite messing up on the above factors (not fair). Anyway, hope to see you at the next CDAS meeting (together with your excess plants and perhaps even a rare plant-ling or two).

 

The aesthetic value of an aquarium depends on harmony between a few basic components that are essential for ultimate success; these are:-

 

  1.  Harmony between the aquarium and its surroundings in the home

  2.  Internal aquascaping

  3.  Plant selection

  4.  Fish selection

 

In the present article, I would like to discuss the plants as they are probably the most difficult aspect to tackle. A knowledge of how to grow water plants and their basic requirements are essential if frequent failures are to be avoided.

 

Water plants are not as difficult as ordinary indoor plants but maintenance of the proper environment for them does involve certain rules. Of course they do not need watering but a lot of observation and some preventive care are necessary, because signs of growing or dying back are always delayed.

 

Once an environmental balance is struck, all is easy, but the most critical and important factor to settle is adequate light intensity. Probably some 90% of tanks with plant problems are illuminated below the minimum light requirements, with poor plant growth resulting. The lighting regime should be maintained at 12-16 hours daily.

 

The other critical factor is the balance of soluble nutrients and trace elements in the water. Excessive concentrations of nitrate can inhibit the growth of plants significantly, as can large fluctuations in composition of the water.

 

Plants respond to any change in their environment, such as day-night period or differences in light intensity, which can influence the water chemistry. The amounts of dissolved oxygen (O₂), carbon dioxide (CO₂) and calcium carbonate (CaCO₃) are not steady. During the daylight hours, the O₂ concentration rises and the C O₂ is lowered by the plants' life cycle. This causes a rise in pH value but at night the process is reversed.

 

The plant function influencing these changes is photosynthesis, i.e., the utilisation of light energy and nutrients by the chlorophyll cells to produce plant growth. In water low in free, dissolved CO₂, plants are able to utilise carbonates, such as Ca(HCO₃)₂ as alternative sources of carbon and oxygen. However, this process generates insoluble CaCO₃, together with small quantities of Ca(OH)₂ and this is particularly the case in hard waters, such as those from natural springs in limestone or dolomite catchments (as occur in continental Europe). In severe cases, the rise in pH and the whole chemical process can lead to the incrustation of plants with a white insoluble layer similar to that often found on aquarium covers, where aeration bubbles burst and dry out.

 

During the night, both plants and fish breathe oxygen and exhale C0₂, which dissolves in the water, forming a weak acid and lowering the pH. The acid reacts with CaCO₃ and Ca(OH)2 and converts them into Ca(HCO₃)₂. This process is essentially the same as that of shell grit buffering, in controlling the problem of low pH.

 

The other major influence on water chemistry is the feeding intensity of the tank inhabitants and the accumulation of waste products. Buildup of nitrogen compounds can be rapid, some of them being extremely toxic. Fortunately, the breakdown of wastes is possible, through the involvement of microbes, fungi, algae and higher plants. Thus the base for a proper functioning of any ecosystem is a biological balance between producers and consumers.

 

 

Nearly all aquatic plants are able to grow emerse (above the water), if the environment is suitable. Under high humidifies, plants grow in the emerse form more rapidly and multiply readily. Some (Typha, ferns, Spathophyllum, Echinoderus, and a number of Cryptocoryne species) grow in rather dry air, but all need very moist ground or frequent availability of water. Many typically 'bog' plants are offered by the aquarium trade as under-water plants, but the problem here is that most of them live under emerse conditions and do not tolerate long-term submersion.

 

All kinds of plants growing on our planet form the basis of all life, because of their ability to utilise inorganic matter and to photosynthesise. Other living organisms are consumers and depend on plants for food, oxygen, shelter and many other needs. Both groups are interdependent in continuing the chain of life.

 

In the case of life in a body of water, each environmental unit, regardless of size (sea, farm pond, aquarium), has to attain a balanced harmony or it will cease to live. Any sudden shock or failure of essentials will threaten or even kill the unit and, unfortunately, man is often the root cause of such disasters, through his poisoning or upsetting the ecological integrity.

 

In any balanced under-water ecosystem we find:

 

  1.  Inorganic components (water, nitrogen, carbon, etc.)

  2.  Organic components (proteins, sugars, fats, humic matter, etc.)

  3.  Climatic influences

  4.  Producers (autotrophs), mostly as green plants, rooted or floating (Spermatophyta), algae or phytoplankton (Thallophyta) in lighted areas and fungi (including moulds, yeasts and bacteria). With fungi, the boundary between producers and micro-consumers disappears, as moulds are strictly heterotrophic: they depend upon organic matter for their energy and can decompose a variety of organic substances to obtain their needs.

  5.  Microconsumers, releasing inorganic matter as nutrients, after utilising protoplasm. These are called heterotrophs but the distinction between them and the autotrophs is beyond the scope of this article.

  6.  Macroconsumers (fagotrophs), mostly living organisms that consume other organisms or disintegrate matter.

 

Plants growing in water, water-logged areas or within the reach of fluctuating water levels, are classified as aquatic. Mostly, they are green, autotropic organisms, generally attached but occasionally free-floating. They do not commonly depend on seed production but are mostly perennial and propogate by means of runners, tubers, buds or stem fragments. Upon decay, they release organic matter into the water.

 

Unlike land plants, aquatic plants are able through photosynthesis, to build their tissue directly from dissolved C0₂ and other inorganic components and trace elements. The water is actually a 'hydroponic' solution, prepared by nature. In many cases, where the plants are totally submersed, the nutrients, etc. are absorbed directly through the leaves, rather than the roots and the latter function merely as anchorages. The 'waste' is free oxygen but during darkness, this is resorbed to a limited extent, with the production of some C0₂.

 

Aquatic plants with stronger root systems would depend upon them for growth under emersed conditions and many species that are generally considered to be under-water growers (Myrioph,yllum, Ambularia, etc.) can develop a low but sturdy emersed growth.

 

With plants with strong roots systems, that undergo regular cycles of submerse and emerse growth, the situation is more complicated. In the emerse stage, the roots are collectors of nutrients and the above-water structures function much as they do in land plants.

 

Plants with floating leaves have air-filled cavities to provide the bouyancy but these are not present in the submerged parts.

 

The most important macro-elements for plant growth are carbon, hydrogen, oxygen, nitrogen and potassium; the essential trace elements include iron, boron, manganese, sodium, copper, zinc and magnesium.

 

Some plant species are able to concentrate particular elements in their bodies: Water Hyacinth (Eichhornia crassipes) absorbs large quantities of nitrogenous compounds. Such plants are useful in biological treatment of waste waters.

 

Nutrients in waters may vary considerably in composition and concentration, according to the natural cycle, the largest fluctuations occurring in rivers and creeks. The larger the water body, the more stable are the levels and so, in the aquarium long term stability is difficult to achieve.

 

Waters with little nutrient (oligotrophic) have less than 0.01 g of dissolved matter per litre and in these, the levels of plankton are restricted and the numbers of fish are low. Oligotrophic peat waters are in this category. Waters rich in organic matter (dystrophic) are usually low in dissolved minerals (particularly Ca ions) but high in humic acids. In such conditions of low pH and nutrient levels, characteristic peat-bog plants are found.

 

Waters saturated with inorganic nutrients (eutrophic) show mostly alkaline reactions and here plants with high nutrient requirements, such as Myriophyllum, Nuphar, Ceratophyllum, Elodea and others grow.

 

Only the halophytes (Najanus, etc.) can tolerate waters with high salinities.

 

In a following article, we shall examine the body structures of aquatic plants.