Heat Cables
Q. I recently decided to put live plants in my 40-gallon aquarium. I've mixed laterite into the bottom half of the gravel (the pieces are 3 to 5 millimeters in size), and above this I added 1 inch of fine gravel (1 to 2 millimeters). Trace elements are added weekly, and carbon dioxide is provided via a solution of baking yeast, sugar and water. The carbon dioxide is connected to the power filter for even distribution. The tank is heated by a 150-watt submersible heater.
With all this done, I've managed to see some growth from my plants. I wonder if I should have gone with a heating cable system for the substrate, but the systems on the market are really expensive. Should I stay with the setup I have right now?
A. Substrate heating can be useful both during the initial period after setup (when it encourages root growth) and for the long-term stability of the tank. On the other hand, it is entirely possible to maintain a top-quality planted tank for upwards of 10 or 15 years without the use of substrate heating. Substrate heating will also not solve problems caused by deficiencies in other areas.
Substrate heating keeps the substrate from becoming chilled and stratified. Set up properly, it also produces convection currents in the substrate that draw nutrients from the water column into the substrate. When the nutrients are drawn into the substrate they are available to plant roots, but not to the algae that grows above.
To prevent the loss of heat through the bottom of the tank, simply set the tank on a sheet of Styrofoam. If the tank stand for an established tank allows access to the bottom glass, you can just tape or glue the Styrofoam in place. If your tank sits on a solid wood stand, the wood itself will work very well as insulation.
Heating cables move water (and nutrients) into the substrate through convection currents, but healthy growing plants can perform the same function. A properly designed substrate in a healthy, heavily planted tank will not become seriously anaerobic (low in oxygen), even without the regular gravel vacuuming done in a fish tank. Understand that slightly anaerobic conditions are necessary for the plant roots to be able to make use of the nutrients in the substrate.
Sometimes, around the three-year mark, a tank that has been growing well and is algae free will begin to have algae problems. This may be a sign that phosphate (and other nutrients) are beginning to leach out of the substrate. This can be alleviated by removing the plants from a third of the tank, thoroughly vacuuming that area and then replanting. Three months later do the next section, and then the final third three months after that.
Many, if not most, aquarists alter their tanks frequently enough (for a number of reasons) that heating cables have very little benefit. Only if the tank will remain set up for an extended period, and all other requirements for excellent plant growth are being met, does it make sense to spend the money on a commercial heating system or go to the trouble of building your own. If the system is well designed you won't be sorry.
If you are struggling to buy adequate lighting and CO2 equipment, I certainly wouldn't spend the money on cables. And let me caution again that heating cables will not solve problems of poor growth in a tank that is not doing well.
Kitty Litter?
Q. I have been told that using a thin layer, about ¼ inch, of cat litter and then using a thick layer of pea-size gravel will help my planted tank. What, if anything, will this layer of litter accomplish for the tank and the plants?
I currently have a 70-gallon aquarium that contains LudwigiaVallisneria and a couple of Java ferns. I currently use a liquid fertilizer once a week. The water temperature is 74 degrees Fahrenheit and the pH is at 7.0. I am new to the live plant aspect of the hobby and would like any advice as to how to keep my plants alive and thriving.
A. While it is definitely true that plain gravel substrates are not conducive to good plant growth, I am not a fan of kitty litter. There are other substrates that provide a better nutrient source for your plants, are easy to use and have an excellent track record. For those who are new to planted aquariums, my advice is to start your tank with a good commercial laterite (or laterite substitute) specifically marketed for aquarium use. Some people complain that laterite is too expensive, but in terms of the total cost of a planted tank, the price is tiny.
If you buy the most expensive laterite available, you will spend less than $20 for an amount appropriate for a 55-gallon tank. If you do feel the need to experiment with cat litter, please be careful that the brand you choose is pure clay, with no added perfumes, deodorants, colorants and so on.
No matter what other materials you add to your substrate, pea size gravel is much too large for good root growth. I prefer gravel of about 1 millimeter in diameter, but good results can be obtained with gravel up to about 3 millimeters in size. For good root development, plan on approximately 3 inches of total substrate depth for smaller plants, and up to 6 inches for large plants with heavy root structures, like Echinodorus and Anubias.
Mix your gravel additives (whatever they may be) into the bottom one-third to one-half of the substrate. Then thoroughly wash the gravel that will go on top in running water. Use at least 1 inch of this very clean gravel to cap the layer containing additives. To fill the tank, place a shallow dish onto the surface of the substrate and very slowly allow the water to fill the dish and overflow. The more carefully this is done, the less cloudy the water will be. When the water level is about 4 inches above the substrate, you can add water a little faster.
Make sure you have adequate amounts of light for the plants you've chosen. Plan on at least 2 watts of fluorescent lighting per gallon, set on a timer to run for 10 and 12 hours a day. If you concentrate on plants that are tolerant of very low light levels (Java fern, Anubias, Java moss and some of the hardier Cryptocoryne species) you could get by with three 40-watt tubes.
Make sure you plant densely right from the start, and concentrate on fast-growing species. Plan on covering at least 70 percent of the substrate with plants, and of that, 70 percent should be fast-growing species. If you can't afford to buy an adequate number of plants at the pet store, you can "pad" your plant budget by purchasing big bags of water sprite, Salvinia or duck weed at a local club auction. All three of these plants grow rapidly and will keep the nutrient levels in your tank in check until you can get the plant mass up to a reasonable level. At that point you can remove most of the floating plants and pass them on to another beginning aquatic gardener!
If your water is quite soft and has a pH of 7.0 or lower, you may do just fine without supplemental CO2. If your water is harder, you may find that your plants do better with a little boost from added CO2. This can be accomplished easily and inexpensively with a pop bottle yeast reactor (AFI, May 1997, p. 36). Finally, make sure you don't overstock the tank or overfeed the fish, or you can end up with serious algae problems.