“Breaking In” the New Aquarist

It’s a done deal. The complete aquarium setup is sold, and the excited new hobbyist, the somewhat less excited spouse, and the previously excited children are gathering up the various components for the trip home. The dealer has explained all the setup basics: placement of the tank, washing the gravel, filling, adjusting the heater, starting the filter, adding the chemicals, fitting the cover and light, and letting the whole thing percolate overnight. There’s only one small, but pretty important lesson to go: “How to Cycle the Aquarium.”

The cycling of new aquariums has been appreciated, if not understood, by American aquarists since at least the turn of the century, when hobbyists realized that fish did better in “aged” tanks, than in recently set up units. And while the concept of the “nitrogen cycle” was well known to biology students much earlier, it wasn’t until the early 1970’s that the aquarium hobby began to fully realize the importance of biological filtration in the removal of fish waste from the aquarium.

Many new hobbyists assume that adding a chlorine or chloramine remover to a newly set up aquarium is all the “conditioning” required. A responsible dealer will take the time to educate his clientele about the basics of the break-in process to protect the customer’s investment and his own reputation and sales potential as well. After all, nothing will bring a new hobbyist’s enthusiasm crashing to the ground as quickly as losing a batch of fish in the first few weeks.

Describing the cycling process needn’t be, in fact shouldn’t be, very complicated – and the use of terms like Nitrobacter and Nitrosomonas should be downright forbidden. A simple, understandable explanation of cycling a new aquarium might proceed like this:

“Fish produce toxic ammonia as part of their waste. In nature and in established aquariums, ammonia is broken down by good bacteria into nitrite, which is only a little less toxic than ammonia. The nitrite is broken down by a second group of good bacteria into nitrate, which is finally much less dangerous. A new, clean aquarium doesn’t have much in the way of these good bacteria in it, and it takes roughly a month to establish both the first and second types. During that time, ammonia and nitrite levels can get quite high, hurting some fish, and killing the more sensitive types, so it’s best to start out with only a few, hardy species until the tank finishes its break-in cycle.”

It should be pointed out that the cycling process will not commence until some ammonia source – either a chemical compound or more commonly a few hardy fish – is added. Some novice aquarists let a newly set up tank run without any livestock for a month, only to learn that they will still go through a break-in cycle when the first fish are finally added. It’s also a good idea to instill in the beginner the idea that the break-in process applies only to newly set up aquariums, or tanks that were excessively cleaned. Once it’s over, it’s over, and elevated ammonia and nitrite levels should never be a problem again under normal circumstances.

Assuming the new hobbyist followed and believed the explanation (after all, everybody seems to have a brother-in-law that just sets up a tank and dumps in $400 worth of discus fish), the next words that leave his lips will likely be:

“Isn’t there any way to speed it up?”

Maybe it’s a sign of the times: in the ’90’s, one does not wait for much of anything. There are rapid transits, instant oatmeal, quick-set cement and express lanes. People don’t want to wait an extra minute to check out at the supermarket, much less a month for an aquarium to break in. There just has to be some technique, some gadget, some technology that allows the anxious hobbyist to get the desired specimens into his aquarium as soon as possible!

At first blush, commercial preparations of “instant cycling” bacteria and enzymes would seem to be the perfect answer for the retailer: a great add-on sale to every new setup that would allow the customer to immediately purchase all the fish they really wanted. Unfortunately, the track record of such products has been rather uninspiring to date. A few people report near-instant cycling of a new aquarium, but most see much less dramatic effects and some seem to go through the same month of elevated ammonia and nitrite levels that would have occurred without the product. Perhaps somewhere in the seemingly endless array of cycling concoctions there are some with precisely the correct blend of exactly the right bacteria – packaged in the perfect container – that will significantly shorten or even eliminate the break-in process. But until we start seeing some independent scientific studies supporting their consistent effectiveness, the wise retailer will be careful not to promise more than can be delivered.

A simpler and more reliable method of speeding up the cycling process is to inoculate the new tank by adding some gravel from an established, healthy aquarium. This gravel undoubtedly will contain live, actively multiplying bacteria of the precise species that consume ammonia and nitrites in aquariums. A dealer can sell or give away handfuls of gravel from his display tanks, taking care that the fish in those tanks are free of any obvious signs of infectious disease. The gravel can be replaced in the dealer’s tank at a very small cost, and the frequent change of those small amounts of gravel actually helps keep the display tanks looking brighter and cleaner. If the gravel color is a match (or at least is acceptably close) to the customer’s own, it should be sprinkled across the top of the unconditioned gravel; if it clashes, the customer may prefer to put the established gravel in a mesh bag or old nylon stocking, so that it may be easily removed later.

Other decorative items, including rocks, driftwood, artificial plants, plastic bobbing diver dogs, and even ceramic Easter Island statuettes can also be used to inoculate new aquariums. Again, these should come from well established, healthy aquariums, and can be used as a temporary or permanent addition to the customer’s tank. These can often be sold for the full retail price, even if they have faded slightly or accumulated a little algae. Once again, the dealer may again find a secondary benefit in the frequent rotation of new decorations into his displays.

The effectiveness of these inoculation methods depends largely on the quantity of bacteria-laden gravel or decorations added. A handful of gravel or a few small stones may help keep ammonia and nitrite levels from reaching the very dangerous peaks, but may only shave a few days off the overall cycling time. Adding about 25% conditioned gravel or a tankfull of plastic plants, on the other hand, may nearly eliminate the cycle completely. If the quantity of conditioned material was insufficient to prevent high ammonia levels, a second inoculation should be considered, as excessive ammonia appears to put the second group (nitrite eating) of bacteria out of commission for awhile.

Perhaps the most reliable method of accelerating cycling time is to add conditioned biological filtration media. (Adding brand new “clean” media right out of the box, bag or bottle will not speed up the cycle, since it’s only providing a space for bacteria to colonize, not the bacteria themselves.) Air operated sponge filters are an excellent choice for smaller aquariums, as are the sponges often used with power heads, and the rotating wheels, foam pads or other biological media used in many popular hang-on power filters. For larger or more sophisticated setups, the spiked plastic balls or blocks utilized in wet/dry filters or sand from a fluidized bed can also be used to inoculate a new system. Of course, the dealer should be careful not to give away too much biological media from any one display tank, putting his own fish at risk.

Since they do contain living things, the cycling potion, gravel, decoration or biological media should not be added until the water chemistry is stable, and certainly not before chlorine or chloramines have been completely removed. After all, these compounds are added to municipal water specifically to kill bacteria. Any pH adjustment or other chemical tweaking should also be completed before the bacteria are added. If the water is safe for fish, it is safe to begin inoculation.

Regardless of the method used, the hobbyist should be cautioned to take things easy at first: a few hardy fish should be purchased initially, and ammonia and nitrite levels monitored. The dealer should develop a list, and maybe even devote a section of tanks to hardy, break-in fish. Many of the mid-sized, pond-raised tetras (including black, white, red minor, pristella, head & tail light, and red eye), barbs (including tiger, black ruby, and the many forms of rosy barbs) and danios (including zebra, leopard, pearl, and giant) are very tolerant of high ammonia and nitrite levels. Some of the tank-raised Corydoras catfish, especially the green and albino varieties, are similarly hardy, and their scavenging abilities may help compensate for a bit of overfeeding by an eager novice. Stocking levels should be one-fourth to one-half the estimated final load for that tank; too low might mean a second, but lesser, cycle when the next batch of fish are added, while too high may result in extremely high ammonia or nitrite levels and loss of some of the break-in fish.

Dealers should certainly have reliable ammonia and nitrite test kits available for sale, and many also offer free or inexpensive water testing to customers who bring in water samples from their aquariums. These should typically be checked weekly if the fish appear healthy, or more often if they seem to be in distress. If the customer is attempting a greatly accelerated cycle, ammonia and nitrite should be checked within a few days after fish are added. Otherwise, it’s possible that the peaks will be missed, and a guess will have to be taken as to whether the break-in process is completed or not yet begun. A tank is only fully cycled when both the ammonia and then nitrite levels have risen and settled back down to zero.

This is also an excellent time to educate the hobbyist in some fishkeeping basics. Stable, tropical temperatures will result in a faster and safer break-in period than cooler or fluctuating water temperatures (some hobbyists actually leave their heaters unplugged during the break-in period to save electricity). Since the beneficial bacteria require oxygen, adequate aeration is required for their reproduction as well as for the health of the already stressed fish. Careful feeding will reduce the risk of rotting food elevating ammonia and nitrite levels even further than normal. And regular partial water changes will help dilute toxic chemicals, protecting stressed fish without appreciably extending the break-in time. the break-in time.

This article originally appeared in

Pet Age Magazine