Stalled Cycle – Nitrates Too High Or Non-Existent after Completed Cycle - An Explanation

Welcome to Simple Reefs. This is a brand new website dedicated to taking the complexity out of Marine Aquarium Ownership. Our goal is to show you how you can own your very own slice of the ocean without spending a fortune. As well as giving you tons of easy to digest information on all things marine. We are still talking about stalled cycles and, today, we are looking at the reasons, and solutions, for why your levels of nitrates may be extremely high or non-existent after your cycle completes.

Is there anything more annoying than a marine aquarium cycle that just won’t finish? You have been adding ammonia for weeks, testing your levels, performing water changes. You are tantalisingly close to being done. Even to the point where you have taken a trip to the local fish shop to pick out a new resident to add to your aquarium.

But there is one problem. One, nagging, little issue that won’t seem to go away and it comes in the form of those damn dirty nitrates. Nitrates are the last part of the nitrogen cycle and the final indicator that our cycling process is complete. But what happens when they are absolutely through the roof or, conversely, virtually non-existent? Well, to explain that, we should take a closer look at the nitrogen cycle.

Nitrate’s Place In The Nitrogen Cycle

We talked about cycling a marine aquarium in our opening article on this subject and, by now, you are probably aware of what the process entails. As well as the importance of the nitrogen cycle (Wikipedia Article) to a healthy marine aquarium.

In essence, we are establishing a bacterial profile, in our tanks, that can process harmful compounds like ammonia. Without the presence of these nitrifying bacteria, ammonia would accumulate and poison our aquarium’s residents.

Ammonia is converted into a less harmful compound called Nitrite by a type of bacteria known as Nitrosomonas bacteria. The Nitrosomonas bacteria doubles in numbers, effectively, every 16-24 hours. Once Nitrites are present in the water, a new type of bacteria will grow that can convert those nitrites into the even less harmful compound known as Nitrate.

Nitrates are the final stage of the nitrogen cycle and an indicator that the process of cycling our aquarium is complete. But nitrates can be a bit of a confusing topic when it comes to testing a newly cycled aquarium. Sometimes they can be sky high and, other times, they can be almost undetectable. There are a few reasons for this. Let’s take a look at a couple of them.

Why Are My Nitrate Levels High After Cycling?

Before we actually answer this question, we need to know something quite important. Do you have nitrites present in your water? If you do, carry on reading. If you don’t, the answer to your problem is quite simple.

Perform a big water change. As big as you can manage but at least 25%. This will take a big chunk out of your current nitrate reading. Keep performing regular water changes until the levels are where you want them or around 10PPM.

If you do have the presence of nitrites in your water, however, we have to approach this a little different. And that involves us talking more about that second part of the nitrogen cycle – nitrites.

The bacteria that converts nitrite into nitrate are known as Nitrobacter and Nitrospira bacteria. Whereas Nitrosomonas bacteria doubles rather rapidly. Nitrobacter and Nitrospira bacteria are not quite as frisky.

These bacteria can take upwards of double the length of time, compared to Nitrosomonas bacteria, to split. This is why we can start to see accumulation of nitrites in our cycling process as outlined in this article right here. The nitrites develop a bit of a backlog while the bacteria is reproducing to levels capable of converting it into nitrates.

Nitrites Can Make Your Nitrate Test Inaccurate

Nitrites can hang around long after our cycle appears to be complete. An aquarium could easily process 2PPM of ammonia in under 24 hours and nitrates could be present indicating the end of our cycle. But nitrites could be stubbornly sticking around. Purely because we don’t have enough bacteria to process them in a speedy manner. This is where high levels of nitrates can come in as the nitrites can be the cause of this problem.

In a lot of commercial marine aquarium test kits, the presence of nitrites in the water will throw off the nitrate test levels. Making it seem as though there are ridiculous levels of nitrates in the water when, in reality, there isn’t. I have experienced this, myself. Witnessing nitrate levels in the 50PPM+ level only a week or so after cycling was, effectively, completed.

Nitrite Levels Can Be Stubborn

Nitrites are less of a concern in marine aquariums due to the fact that saltwater contains high levels of the mineral chloride. The nitrites in the water won’t be absorbed into your fish’s bloodstreams. Both chloride ions and nitrite ions compete for the same real estate on your fish’s gills. Only, there is far, far, more chloride in saltwater than there is nitrite. Meaning the nitrite really doesn’t get a chance to become deadly.

In freshwater, the opposite is true. There is virtually no chloride so any nitrite that is in the water will, almost certainly, be absorbed into the fish’s bloodstream. Where it will, in turn, bind to the Haemoglobin, transforming it into something known as methaemoglobin. Whereas Haemoglobin carries oxygen around the body, methaemoglobin does not. Essentially leading to freshwater fish suffocating.

With this in mind, it is far more common for saltwater fish hobbyists to ignore levels of nitrite when it comes to their aquarium cycle being complete. Many, simply, look at the level of ammonia and whether the tank can process 2PPM ammonia in under 24 hours. If it can and it can do this consistently, they consider the cycle complete.

The nitrites are incredibly stubborn, however. It can take months for there to be enough Nitrobacter and Nitrospira bacteria present to deal with the backlog. Meaning, for this entire time, your nitrate test results will not be accurate and may show ridiculously high levels that aren’t representative of your real levels.

Nitrates Aren’t Very Harmful

It’s not a solution to your high nitrate problem, as such, but it is worth me mentioning that nitrates really aren’t that harmful. In fact, at this point in your marine aquarium adventure, you likely don’t have any coral and the residents in your aquarium are pretty limited. With this in mind, it would pay to try not to worry about it too much.

The nitrate levels should drop organically and they shouldn’t do any harm to any of your aquarium’s residents, at this stage. They may fuel your uglies, though, so you might want to do what you can to bring them down a bit. Just try not to let it become a number that you chase for the next six weeks as that can become a very bad habit in marine fishkeeping.

What Can I Do To Drop The Nitrate Levels?

If you are concerned, there is a plan of action that we can take to drop those nitrate levels down. We will also, in turn, be addressing the nitrite levels by bolstering our bacterial profile to help cope with them. Let’s lay out a few steps.

• Perform a large water change of 25-50%
• Give your bacteria a boost with some bottled nitrifying bacteria

Performing a decent sized water change is going to bring those nitrite and nitrate levels down immediately. We are then going to buy a bottle of nitrifying bacteria. This bacteria contains everything we need to complete our nitrogen cycle. Naturally, our tank is cycled so we already have a nitrogen cycle but we are going to bolster it and give it a boost.

Follow the instructions on the bottle. Adding bacteria every day and performing regular water changes, perhaps even every few days. You should quickly see the nitrate levels begin to drop. Eventually, there will be enough bacteria to process the excess nitrites and your nitrate levels will start to look much more normal.

With all of this being said, don’t worry too much about nitrate levels being high. High nitrate levels don’t indicate a stalled cycle. They are simply the final piece of the puzzle and they can look a little wonky for a few weeks while your brand new cycled aquarium settles down.

My Nitrate Levels Are Non-Existent After Cycling?

This is a bit of a strange issue that I do see fairly frequently. There is one simple answer to this problem, though, and it comes in the form of a question. Is your aquarium processing the ammonia you are adding to the water? Can it remove 2PPM of ammonia from the water in under 24 hours? If it can, your cycle is complete.

The nitrates will be there, without question. They are the end stage of the nitrogen cycle so the sheer fact that your aquarium is processing ammonia means that the cycle is taking place and the nitrates will be the biproduct of that. They are, most definitely, there even if the test isn’t picking them up.

Again, nitrate test results, during and after cycling a marine aquarium, can be notoriously unreliable. That’s without mentioning how poorly most commercial nitrate tests can detect low levels of nitrates. You probably just have very low levels and don’t have a single thing to worry about.

If you have been performing water changes, you will have been removing the nitrates from the water. Hell, if you have already started using a protein skimmer then that might be the reason you aren’t seeing any nitrates. Don’t worry about it, you are fine! If ammonia is being processed and removed from the water as confirmed by your test kit, your cycle is not stalled, it is complete. You are done and ready to proceed but always go slowly.

In short

High nitrates or very low nitrates aren’t a huge problem when it comes to cycling a marine aquarium. The presence of nitrites can throw nitrate tests off, making them read extremely high when, in reality, the levels are normal. You can perform a few water changes to drop the nitrate levels and add some bottled nitrifying bacteria to help things along or just wait it out.

Low nitrates are not an indicator of a failed or stalled cycle. As long as your aquarium can process 2PPM of ammonia in under 24 hours, your cycle is complete and nitrates will be present even if a test doesn’t show that. Thank you very much for reading and spending your time with me on Simple Reefs.