

all 9 comments

[–]defenderTX 5 points6 points  (5 children)

You need to understand the nitrogen cycle. Research it, learn it, love it. Understand why it's important to aquarists and how you establish a biological filter. It's intimidating at first, but once you have it you can really get started with aquaria.

[–]asanf91[S] 0 points1 point  (4 children)

I've been reading into this, and I feel like its either hit or miss.. It either works, or it kills everything..

[–]defenderTX 2 points3 points  (1 child)

Okay, I've been thinking about this and the fact that you think it's hit or miss tells me you're being lead astray somewhere. Originally, I figured just saying that the Nitrogen cycle was important and letting you go off on your own was fine but the truth is it's a Monday morning at work, I love talking aquaria, and I'm feeling extra verbose. So I'm going to go into the Nitrogen cycle real quick and hopefully get you back on track.

The Nitrogen Cycle

What do all living things create? Waste. It's something you probably don't think about if you're a newbie to keeping fish because with other pets there are well defined ways of removing their waste. With cats you clean the litter box. With dogs you pick it up in a little baggy and toss it. With fish, however, the waste readily dissolves into the water. So what happens to it? Out of sight out of mind? Nope. The organic compounds in the waste go through several transformations in what is referred to as the nitrogen cycle, and it all starts with Ammonia.

Ammonia (NH3)

Ammonia is produced as a byproduct of fish metabolizing protein. Proteins in the food that fish consume are made up of amino acids and each amino acid has an amine group which contains, you guessed it, ammonia. When the fish gets rid of excess nitrogen from the protein it consumes it does so in the form of Ammonia. Fish (and invertebrates) are constantly leaching ammonia into the water from their gills and through their waste.

The problem is that Ammonia, even in relatively low concentrations, is toxic to most life when inhaled. If you inhaled Ammonia vapors it would burn your throat and lungs and when fish breathe ammonia through their gills it burns them in the same way. So how do you get rid of Ammonia if it's dissolved in water? You need something to consume it and luckily nature has evolved the perfect method.

Nitrite (NO2)

With all this excess nitrogen dissolved in fresh water in the form of Ammonia, you know some organism was bound to evolve to take advantage of it. That's where Nitrifying bacteria come into play. Nitrifying bacteria consume inorganic nitrogen compounds for energy including Ammonia. Nitrifying bacteria turns Ammonia into another toxic molecule - Nitrite (NO2). The specific way it does this is called Ammonia oxidation by autotrophic nitrification. Notice that Ammonia contains no oxygen in the molecule before the oxidation but Nitrite does - two Oxygen atoms to be exact. We don't really care very much about Nitrite because it's an intermediary step. The exact same class of bacteria that convert Ammonia to Nitrite will convert Nitrite to it's final form: Nitrate.

Nitrate (NO3)

By adding an extra oxygen atom to Nitrite you get Nitrate which is much, much less toxic to fish and living organisms. Nitrifying bacteria will also perform this final step in converting fish waste into something that is only toxic in high concentrations, like above 5 ppm (part per million). Not only is Nitrate less toxic to fish than the first two molecules but it has an added benefit: it's plant fertilizer. Plants utilize the Nitrogen atom in Nitrate to satisfy the need for one of it's main macro-nutrients.

If Nitrate is still slightly toxic to fish in high concentrations then how do we remove it? That's where weekly water changes come into play. Replace roughly 20% of your total water volume with new water weekly and it will remove enough Nitrates that they stay below a level that's considered stressful for the fish. In my saltwater reef I do weekly water changes and am able to maintain a Nitrate level that is undetectable by Nitrate test kits.

Cycling Your Tank

What does it mean for an aquarium to be "cycled"? It simply means that your biological filter is established and contains all of the proper bacteria to complete the Nitrogen Cycle I described above. Most people new to aquariums think that a water filter contains some type of physical or chemical medium to "purify" the water. While that's sometimes true, most of the time the filter provides an area with water flow and a porous media that bacteria can grow on. In aquarium keeping we're always worried about this bacteria - it's the most important thing in your tank.

How do you know the status of your biological filter and the bacteria inside of it? That's where your test kit comes in. If you haven't already, go to a pet store and pickup an API Freshwater Master Test Kit. You need it to determine where you're at in the cycle and to make sure your Nitrate levels are adequate later down the road.

So, how exactly do you get the nitrogen cycle started without subjecting fish to high levels of ammonia that will burn their gills? Fishless cycling. It's all the rage right now. You see, fish aren't the only way you can get ammonia in your tank. The food that the fish eat that produces ammonia as a byproduct can produce ammonia all by itself with a little help from other bacteria that consume the proteins in the food. Drop a raw shrimp from the store in the tank and leave it for a week. Bacteria will start to consume it releasing Ammonia as they go. The biological filter will establish and when you read Nitrate in the test kit you know you're ready to go. Remove the raw shrimp, do a water change to get Nitrate back down to acceptable levels, and add your fish.


I once heard from a wise reefer that reef keeping isn't about keeping fish and corals, it's about keeping water. It's literally a hobby dedicated to water quality. If you maintain the proper water parameters the fish and coral (or plants) will take care of themselves. This isn't like having a dog or cat where their natural environment is only slightly different from your house. The natural environment of a fish is radically different than what most people understand. You're trying to recreate that natural environment as best as possible - that should always be at the forefront of your mind.

Was that a lot of text? Yes, sorry! I'm sure you're thinking something like "Cmon, not even kid that buys a fish from PetSmart knows all this stuff!", and you'd be right. You don't necessarily have to know all of this to keep fish alive. You do have to know all of this to keep fish as healthy as possible and have long term success in aquaria as a hobbyist.

Anyway, if you made it this far, enjoy your new hobby and feel free to PM me with any questions.

[–]garythecoconut 0 points1 point  (0 children)

Wow very helpful! thanks!

[–]rach3121 1 point2 points  (0 children)

If you understand it and cycle your tank properly, then maintain it, you shouldn't run into many issues. It definitely isn't hit or miss.

[–]defenderTX 1 point2 points  (0 children)

Yea, it definitely shouldn't be hit or miss. The important thing is that you cycle your tank properly and then maintain it. I'm assuming your talking about freshwater here, if you're wanting to dive into saltwater the nitrogen cycle is just the beginning and I would recommend trying your hand at freshwater first.


Not being a smartass, but googling "aquariums for beginners" will show you many answers.

[–]asanf91[S] 0 points1 point  (0 children)

haha i completely understand. I just spend too much time on reddit to not have asked here as well.

[–]Weagle_NC 1 point2 points  (0 children)

You'll need the API Master Test Kit.
You'll need Seachem Prime to treat your tap water.
If you need a filter, I'd recommend the Aquaclear 30.
If you need a heater, get a heater rated for about 50w (Jager, Aqueon Pro Series are good brands).
Decide what you want on the bottom of the tank (sand, gravel, ecocomplete, etc).

Refer to the Fishless Tank Cycling guide on the sidebar. Either find ammonia at Ace Hardware or similar store or use fish food for ammonia. If you can get any filter media from a friend's filter, it will help kick start your aquarium. While waiting for the tank to cycle, you can research what can go in a 10 gallon tank.

Once started, I'd recommend a 5 gallon bucket for weekly water changes. Only use it for your fish tank and nothing else.