When you set up your aquarium, when you add the gravel and decorations, attach the filter and heater, and add water conditioner (a solution that removes chlorine from tap water) you may want to go out to the nearest aquarium shop and pick out as many tropical fish as you can.
Stop right there! That’s the number one mistake people in the aquarium hobby make!
Remember those beneficial bacteria we discussed in Aquarium Care 101: Part 3? Well, until you provide them with a food source (fish waste), there is no bacteria in your aquarium (because they have nothing to eat). So, a brand new fish-tank has no beneficial bacteria in it!
In fact, during the first month or so of your aquarium’s “life,” the cleanliness of your aquarium water may degrade quickly if you’re not careful.
In particular, any tropical fish you add to a newly set up aquarium will produce more waste than the still growing beneficial bacteria population is able to consume. You, therefore, have to be very careful so as to not add too many fish in at once. In so doing, you’ll give the biological filter time to develop and do its “magic.”
Just to review, let’s take a quick look at the biological filtration process one more time:
Ammonia, the highly toxic substance that all fish release, is converted by a group of beneficial bacteria (known as Nitrosomonas) into Toxic Nitrite. Nitrite is then taken up by another group of beneficial bacteria (Nitrospira) and converted in Harmless Nitrate.
This two-step biological filtration process looks like this:
higly toxic Ammonia → toxic Nitrite → harmless Nitrate
But remember, brand new aquariums have no beneficial bacteria in it!
That’s why you should not add all the tropical fish into your aquarium at once. Doing so would cause a sudden and high influx of Ammonia into your fish-tank. Very high levels of Ammonia will kill your fish!
You should therefore add the fish in batches in order to give the beneficial bacteria time to multiply to sufficient levels – to a population that can handle the amount of waste being produced! Once the beneficial bacteria has multiplied to a healthy level, you’re ready for the next batch of tropical fish. This process is known as ‘cycling the aquarium’ and takes anywhere from 4 to 6 weeks to complete.
You may say, “yeah, but I have a giant filter attached to my aquarium!” Well, keep in mind that no filter (which relies on mechanical and/or chemical filtration alone) can match the cleaning power of nature’s little workers. Let me say it again, NOTHING can substitute the work done by beneficial bacteria!
So, you indeed do have to add your fish in batches. Most aquarists recommend keeping one inch of fish per gallon of aquarium water, though in the Aquarium Care eBook, I recommend a slightly smaller ratio. But, if you go for the one inch of fish per gallon rule, a 40 gallon aquarium, for example, has a maximum stocking capacity of 40 inches worth of fish.
So, how big should your initial batch of fish be? Most people recommend adding 20% of your aquarium’s total stocking capacity. If you have a 40 gallon aquarium, your first batch should not exceed 8 inches worth of tropical fish (again, 8 is 20% of 40).
I don’t mean to scare you, but failure to properly ‘cycle’ your aquarium most likely will result in the death of all your fish! This ‘cycling’ process does require a bit of patience, but it’s well worth the time!!!
Note: In the “members area” there’s a 10 minute *video* that describes exactly, down to every detail, how this biological filtration process works and how you should cycle your aquarium so that your fish don’t die within the first week. The video is based on the expert Aquarium Care eBook found here.