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Silent Cycling in a Planted Aquarium
Aquarium plants are your friends - and ammonia's mortal enemies!

 Age of Aquariums > Aquarium Articles


Every new aquarium setup must go through a cycling period. What does that mean? It is a process that builds up a beneficial bacterial colony in the filter media and the gravel. This bacteria converts harmful ammonia and nitrite into nitrates, and until a large enough number of nitrifying bacteria is reached in a new tank, the ammonia and nitrite levels will spike to toxic, even deadly levels for most fish. The process takes up to 30-60 days to complete (depending on the water temperature and other factors). In part due to lack of information, in part due to the anxiety of looking at an empty tank for 1-2 months, even today many people simply go ahead and add a whole bunch of fish to newly setup tanks anyway, many of which end up dying during, or not long after, the cycling period.

However, to the responsible fishkeeper, subjecting fish to this situation is not an acceptable practice. There are traditional methods called fishless cycling where fish food, a small piece of prawn, and/or pure ammonia is added manually to begin feeding the bacterial colony. This is a necessary method in non-planted setups. But I read a lot of forum stories around the net were aquarists seem to be very confused with the fishless cycling method. I don't blame them. I was once confused with the same thing also. Some frequent questions are: "Where can I find ammonia?", "How many spoons of flake food should I put in?", "There is already a big flake mess all over my tank!", "My nitrite is taking too long to spike, what's wrong? Should I add more ammonia?" "My ammonia spike is over, should I continue adding ammonia?", "When will I be able to put the fish in?", and so on.

With planted aquariums, if a few measures are taken, there is no need for fishless cycling. With the method described here you can forget about adding ammonia, flake food, raw prawns, etc. There is a better and quicker way to start your planted aquarium, such that ammonia and nitrite remain completely "silent", because they don't spike at all!

Silent Cycling

Since the plants consume ammonia and nitrate as nitrogen source, there is no preliminary need to build up nitrifying bacteria as long as there are enough plants growing well from the start. Cycling is all about building up ďsomethingĒ that can prevent deadly levels of ammonia and nitrites in the why not plants? They don't just perform that function well, they look much better than an empty tank! They allow the addition of fish much sooner at little to no risk, and with time, there will always be a natural build-up of bacteria in the filter with or without our help. Preparing a new tank for silent cycling is very similar to following standard procedures for any tank intended to have live plants in it, with just a few extra precautions. Let's see what is necessary in order to guarantee a proper silent cycling of a new tank, and I will exemplify with my 180 L planted community tank during the description:

Step 1 - Substrate and filter power-up
Place the tank in a secure position where it wonít be hit by direct sunlight. Direct sunlight will trigger an algae bloom and, believe me, this is the last thing you want. Add a first layer of fertile substrate if you choose to do so, then rinse some gravel well and place it over the fertile layer. Try to build up 7-12 cm of gravel like a bank, thicker in the back, of course. Fill up with water and treat with the dechlorinator (chlorine, chloramine and heavy metal remover). It is going to be dirty for a day or two, but the filter circulation will eventually clean it. Plug in the power filter and heater. Let it run for 24 hours, taking this time to make sure everything is working correctly and to set the temperature at the right level, for example, most tropical fishes and plants do well at about 24-26įC.

Step 2 - Adding plants and making sure they grow
On the second day, or whenever you're confident everything is OK, plants should be added. Over 50% of the gravel surface has to be planted with fast-growing stem plants. Among the best ones I can recommend from personal experience are:

  • Ceratopteris thalictroides,
  • Hygrophila polysperma,
  • Bacopa australis,
  • Egeria densa.

But there are certainly others. For more information about these and other plants, browse the Garden section of this site. When planting, make sure to remove all the old leaves and some of the old looking roots. Don't worry, you won't harm them and it will encourage growth. Plant the stems about 2-3 cm apart from each other, so all of them have enough light, which is essential for good plant growth, without which the silent cycle won't work.

After the plants are added, if you chose not to use fertile substrates, you need to at least stick one iron rich gravel fertilizer tablet or granule (ask your pet-shop) into the gravel beside each plant. The gravel fertilizer gives the plant a head start while the algae canít use it since they do not have roots. Liquid fertilizer is not a good option in the beginning.

CO2 injection is a must have and there are many ways to introduce it. The DIY CO2 yeast reactor, pressurised CO2 system (could be expensive) and CO2 tablets with a plastic reactor-diffuser (ask your local pet-shop).

Lighting should initially be low to medium, between 0.3-0.5 Watts per liter for fluorescent tubes. Strong lighting (over 0.8 W/L) requires the use of pressurized CO2, otherwise an algae break-out is very likely. To achieve full efficiency of your fluorescent tubes, reflectors should be placed over the lights (tip: I used kitchen tin-foil as a reflector). Without good reflectors, the amount of light that actually enters the water can be as low as half of the total light generated by the tubes.

So thatís it, we have fast growing plants; iron rich gravel fertilizer, CO2 injection and proper lighting. After all this is done, it's time to sit back and observe the plant growth for a few days. We need to be sure, before adding any fish, that the plants are thriving and growing well, which means they are being capable of uptaking any ammonia from the water. During this period, it is highly recommendable that you test the water occasionally and make sure the ammonia and nitrite levels are really kept at zero. Otherwise you will put our fish at risk and make the algae happy.

Step 3 - Introducing the first algae eaters
About two weeks after the tank has been planted and if they are showing good progress, you can start adding fish - and algae eaters should go first. For my 180 liter tank I added 2 Siamese algae eaters and 3 Otos, but there are several other options and a separate article will soon be available in this section, dedicated to the "algae eating army." Before adding the fish, I suggest doing about 20% partial water change (always use the dechlorinator). Donít feed the algae eaters! Let them take care of the minor algae. You will probably experience some brown, hair, red and thread algae, which these fish will consume. Any mature algae should be removed manually, as these fish prefer to feed on young algae.

Step 4 - Increasing the population
About one week after the algae eaters have been added, you can start adding your other preferred species. This has to be done gradually like with any other type of cycling, and it's always recommendable to do a partial water change just before adding a new group of fish. In a typical medium sized tank (80-200 liters) you should add about 5 small fish at a time. I added more algae eaters, 5 Amano shrimp. Again, I did not feed them as they will feed on algae. Just because you donít see the algae it doesnít mean that there isn't any. After another week, you can add 5 more fishes, and so on until you're happy with the population. I added 2 golden angelfish, and on the following week 11 cardinal tetras. Once you start adding non-algae eaters, start feeding accordingly. As always, don't overstock your tank there is no need for it! Instead of falling into the temptation of "having" a whole bunch of random fish that just exist in your tank, learn to appreciate the natural behaviors of properly kept ones and the joy of "keeping" them throughout their natural lives of many years. overstocking and mixing incompatible species will only trigger diseases and disasters. Imagine yourself living in a small, dirty apartment with 20 more people who don't even like you. With shoaling species, it is much nicer to have a bigger group of the same species than many small groups of different species. Let them have a good, long fish life in your tank!

Step 5 - Establishing a fertilization and maintenance regime
After about 4 weeks since the day you added the plants, it's time to start adding liquid fertilizer. It's better to use only half of the recommended dosage for the first few weeks. If your plants show no yellowness, there is no need for more fertilizer, and if they're showing deficiency symptoms, add the recommended measure. I use Tropica Master Grow and I dose 25 ml every week, since all my plants are fast growers. Slower growing plants need less nutrients.

Typical Nitrate (NO3) levels for planted tanks should be around 10-20 ppm. Your fish population might already supply enough through excrements to reach this level, but with planted tanks you will often need to supplement. Nitrate can be added through KNO3 (Potassium nitrate) and NaNO3 (Sodium nitrate). The first one is better to use since it contains Potassium, which plants also consume in large quantities. Many aquarium gardeners also use a home-made solution known as PMDD (Poor Mans Dosing Drops) which you can learn about and even order from the internet.

The best fertilizing and maintenance regimes depend on many things, like how strong the lights are, if pressurized CO2 is added, how big the fish bioload is, how big plant biomass is and how many of them are fast growing ones. To be sure how to manage your own regime, the best way is to ask questions and exchange experiences with other hobbyists, for example on aquarium forums. For my 180 liter low light aquarium, I dose 10 ml of each PMDD mix on weekly a basis + 10 ml of Tropica Master Grow for iron dosing. I also connected two bottles of DIY yeast CO2 (one bottle per 90 liter) to the filter outlet. I do 25% weekly water change.

In summary, I find silent cycling a very natural way to start an aquarium, with a beautiful tank decoration resulting as an added bonus. In fact, if you have doubts on how to aquascape your tank, take a look at other people's tanks in the Tank of the Month section for ideas and inspiration. Remember, our hobby can and should be joyful, rather than frustrating. Happy fish/plant-keeping! :D

Dusko Bojic
Learn more about the author's
aquariums at his blog Aquarium Poetry
All photos copyright © Dusko Bojic and displayed here with his permission.
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