Top 10 Mistakes New Fish Owners Make #9

The #9 Mistake – Adding Fish Too Early

You have a plan, you got your tank and all the additional items, so it’s time to add the fish! But how many fish do you add? In what order do you add them? In the beginning, your biggest hurdle will be establishing your nitrogen cycle. This cycle is made up of commensal bacteria living in your substrate and biological filtration media (sponges, matting, bio balls, ceramic cubes etc). These helpful bacteria convert the primary fish waste of ammonia into nitrite and from there into nitrate. Ammonia and nitrite are highly toxic to fish, and can cause lethargy, loss of appetite and death.

When a tank is brand new, the bacteria have not been colonized. There are many commercial starters promising to “instantly start” your tank, but they are the aquatic equivalent to snake oil. Our office tested over half a dozen of these products with no decrease in time to conversion. You do NOT need to add these products to your tank, they will come with the fish; they just take time to become established. It will take 4-6 weeks for your tank to go through all the necessary steps to become established. If you follow your tank’s progression with your water quality testing kit, you will yield a graph like this:

You will see spikes in ammonia, nitrite and then nitrate. When you see this DO NOT PANIC. It is a normal occurrence in EVERY new fish tank. It is called “New Tank Syndrome” and there is no way around it unless you have another established tank with similar water parameter requirements that you can steal some filter media from.

The best way to combat New Tank Syndrome and avoid crashing your tank with a major ammonia spike is by starting with just a few fish in your new tank. Start with one or two goldfish or 3-4 tropicals, like zebrafish or tetras, before your tank is established. Slowly increase your fish levels from there and you will never have an issue.

Be patient! It is extra work, but I guarantee by following these steps, you will not lose a fish from New Tank Syndrome. Buy a test kit, know how to use it and don’t panic when those spikes hit. By having fewer fish in a larger volume of water, you will produce a smaller, more tolerable spike, keeping your fish alive.

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The Nitrogen Cycle

The Nitrogen Cycle

As you may well know, water quality is a significant aspect of pet fish health. Like the air we breathe, the water a fish swims in is directly linked to their overall health. As a fish veterinarian, we routinely test the water our patients swim in for various parameters. We discussed pH and kH previous, so today, let’s look at the nitrogen cycle.

As you may notice, the traditional nitrobacter and nitrosomas bacteria species have been omitted from this diagram. This is due to the fact that there are just SO MANY different bacteria species involved in nitrogen-fixation, that we cannot simply define them in these two genuses.

In a fish tank, a fish’s primary waste is ammonia. Ammonia is produced by the breakdown of protein, the main staple of most fishes’ diets. Ammonia is excreted out through the urinary tract and gills. Ammonia is highly toxic to fish, causing death and increased secondary illness, so it is converted, through nitrogen-fixing bacteria, into nitrite. Now, nitrite can be just as bad as ammonia. Methemoglobinemia, or “Brown Blood Disease,” is caused by a build-up of nitrite. Nitrite can bind to hemoglobin in the blood and outcompete oxygen. This causes a brown coloration and the fish will asphyxiate from lack of oxygen. Thankfully, more nitrogen-fixing bacteria convert nitrite into the final nitrate. Nitrate is safe for fish at low levels, but at higher levels, and depending on the fish species’ tolerance, can cause the same issues as high ammonia. Nitrate is removed from the system by aquatic plants or water changes.

In established systems (over 2 months old with no new fish or equipment), your ammonia should be ZERO. Most low readings indicate your filtration capacity is inadequate or secondary to overfeeding. The highest reading acceptable on our test kit is 0.1 mg/L. The traditional API freshwater master test kit ranges between 0-0.25, so attaining a 0.1 reading will not occur. Due to the broad range of values, a 0.25 reading may be a false positive (reporting a higher value than what is actually present).

There are many commercial additives for removing ammonia from your tank prior to the nitrogen cycle. Some can cause ammonia test kits to read falsely high. These additives are short-term solutions that should only be used with significant health issues. They are not a long term maintenance solution. You MUST establish your biological filtration (good bacteria) for long-term fish health. If you have persistent ammonia in your tank, consider the following solutions:

  • Is your filtration adequate? Tanks with higher bioloads (size and number of fish) will require more than standard filtration. When in doubt, always filter more than you should.
  • Are you feeding appropriately? Remember, ammonia is produced from breakdown of protein in a fish’s diet. More food = more ammonia. Check your protein levels! For more information on fish diets, read this.
  • Are you doing lots of water changes? If you are constantly removing ammonia, your nitrogen-fixing bacteria will never become established.
  • Is there ammonia in your source water? Check the level coming out of your tap or well to make sure! You may need to consider another water source.

There are also commercial additives that will “quick start” your nitrogen cycle. Sorry folks, but these are a complete scam. With the exception of one product that slightly shortened the establishment of your nitrogen cycle, it will take 4-6 weeks MINIMUM to get your tank properly cycled. By “cycled,” we mean the establishment of a complete nitrogen cycle with ammonia being converted all the way to nitrate. We recommend starting with very few fish and monitor your ammonia, nitrite and nitrate levels carefully!

If you have any more questions about fish and nitrogen cycles, please comment below.