Nicold Aquaria - Cycling Madness

Cycling With Fish - Are You Mad?!
(Dispelling the myths)

The main reason that people cycle with fish is that they are not aware of fishless cycling or think that it's difficult - I give the benefit of the doubt in that I don't believe that people cycle with fish because they like to stress and damage them...but you never know.

Why cycle with fish? Mostly it is through necessity. An aquarium is purchased without really much thought going into it (I've done it), bung some fish in and then they get ill. You follow the LFS instructions and do lots of massive water changes and then everything is better. Voila - one cycled tank, without even realising it. This pattern of behaviour is then repeated for every tank that is purchased until an alternative is shown, like seeding from an established tank.

Cycling with fish is obviously visually more interesting than fishless - but when you decide to keep fish you are taking on the responsibility of looking after these lives to the best of your ability. This includes limiting the amount of stress that they are put throug . Cycling with fish puts the fish through immense strain in the forms of ammonia and nitrite spikes (when the concentration of ammonia and nitrite in the water rises above safe levels and then recedes). Ammonia and nitrite poisoning causes permanent damage, even in low concentrations. The majority of damage is to the gills. As NH3/NH4+ or NO2 molecules pass over the gill plates the areas involved in gaseous exchange (taking oxygen out of the water) are literally burned away. It would be like us breathing dilute sulphuric acid. Once the gills are damaged they will never regain their original capacity and the result will be a runt (incapable of reaching its full potential in size or health).

Myth 1 - hardy fish

The most common fish that people use for cycling seems to be goldfish (Carassius auratus) and danios (Brachydanio ..) believing that they are somehow "hardier" than other species. But are they?

No, they're not. All fish have the same basic nervous system and all fish respond to the same pain impulses. Ammonia and nitrite poisoning will affect all species of fish the same way as described above. The difference is that Carassius auratus and Brachydanio can tolerate poor conditions for longer than more sensitive fish (Carassius auratus and other lake dwelling members of the carp family are capable of oxidising ammonia in the brain - but this is for temporary survival and shouldn't be imposed upon them). Is that a contradiction? No it is not. The fish will still have permanent physiological damage, just any other fish that is subjected to ammonia or nitrite poisoning. The ability to survive does not indicate hardiness in my book.

Humans are capable of withstanding vast fluctuations in our environment and adapt to them - we are hardy. A fish cannot adapt to having it's cell membranes burned away - the ability to survive such an event does not indicate hardiness.

Myth 2 - feeders and other 'disposables'

Many of the people who continue to cycle with fish use so called feeder fish - things like guppies (Poecilia reticulata) and goldfish (Carassius auratus). These fish are considered feeders for one reason only - they are prolific, and subsequently they are cheap to buy.

The fish does not know that is is a 'feeder'. As far as it knows it is a regular fish, swimming about to achieve its ultimate goal of reproducing, just like all animals.

'Feeder' is a term that we have bestowed upon such fish, yet such fish are other peoples pets. I keep goldfish, a friend of mine has guppies - we would never think of feeding our fish to another animal, but we also accept that the species that we keep do end up in the stomachs of Oscars and Arowanas all over the world.

Just because they are classed as 'feeders' does not mean that they should be afforded any less respect than the fish that will eventually inhabit your aquarium. Many times I have read people say that they use feeders to cycle their tanks because they are disposable.

They are fish, just the same as any other fish that you would buy. They have requirements, and they feel. Labeling something as disposable does not make it so.

'Feeders' are very rarely second rate fish and should not be treated as such.

Myth 3 - Bacteria colonies

It is commonly thought that once there are zero levels of ammonia and nitrite and detectable nitrate in a tank that it is cycled and you can add the fish that you want to your tank. Fine, there is a bacteria colony there that will deal with ammonia and nitrite. But how much will it deal with?

If you cycle with fish you'll probably do one of the following: a small school of danios, a couple of guppies, or a goldfish or two. You check the water parameters until you have 0ppm NH3/NH4+, 0ppm NO2, and (x)ppm NO3. You get rid of your 'feeder' fish in whatever fashion best gets you off.

Before you add your fish have you ever thought about what your newly established biofilter can handle? You've stocked your tank and some of your new prides and joy are ill...how come? The tank was cycled right? Wrong!

The tank is cycled and will accommodate a bioload less than or equal to the fish used to cycle it. So a 60 gallon tank cycled with one 2" goldfish will have a biofilter that can only immediately sustain the same amount of waste as is produced by one 2" goldfish. If you were to add 6 cories, and a dozen barbs (this is an example) then all of a sudden there would be huge ammonia spike followed by a huge nitrite spike as the bacterial colonies reproduce to cope with the demand. In the meantime, your nice new fish are slowly dying in exactly the same way as the 'feeders' before them.

By fishless cycling you can create a bacterial colony that is much larger than cycling with fish. A colony that is able to cope with any bioload you choose to introduce. Fishless cycling stops unnecessary suffering to fish, and to fish that are subsequently added.

Whenever you add fish to a tank, even in an established tank, there will be a ammonia/nitrite spike. However, with a mature bacterial colony the spike is not as dangerous to fish as the bacteria multiply in greater numbers.

It is important in any tank not to 'dump' a lot of fish in all at once otherwise the spikes will be exponential causing damage, stress and illness to your fish (commonly called crashing).

It is also possible to 'seed' a new tank from an established one by taking some of the filter material or the top level of substrate (where the majority of the nitrifying bacteria live) and placing this in the new tank. This creates a starter colony that will adapt to the bioload.

One thing that you should consider is cost - fishless cycling can be done for free, even a bottle of ammonia is cheaper than fish (you can also cycle hundreds of average sized tanks with one bottle of ammonia - how many tanks can you cycle with the same fish?).