New Tank Nitrate Level 0


HI just set up a 25l tank 2 days ago. Put some plants in and turned filter and heater on. Put a little fish food in aswell. Just tested the levels and ph is around 6.4 nitrate , nitrite and ammonia levels are all 0. Is this good and when could I put fish in?

Mick Frost

0 Ammonia is only a good thing at the end of the cycle. The fish food method of fishless cycling can take 2-3 months. A quick search on the Nitrogen Cycle would be the best place to start.
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I would wait a little while before putting fish into the tank, at least a week or so. Usually, its best to wait around 3 weeks for the tank to cycle before adding fish. Its good to have everything at 0 when you add fish, which will happen after the tank cycles. You look in a good spot, 6.4 PH is pretty low though (acidic) angelfish, tetra and a few others like it soft like that. Typically an 'average' for PH is about 7.4. PH is relative though, and won't totally matter until you've decided what fish species you're going to stock.

If you want, you could do 2 things as of right now to jump start the cycle so you don't have to wait too long.

You could grab a live bacteria supplement and dose the tank according to instructions and test weekly. You could also potentially add a few (maybe 3) hardy and small starter fish after adding bacteria, just to get the tank going (though this is considered cruel, the fish would undergo more stress this way than if you waited the entire 3 weeks and then added a few.)

Your tank may start to get cloudy in the next couple of days, when you notice that, leave the tank alone (don't do a water change). As this is the 'good bacteria' of the nitrite cycle starting to colonize in the tank.


All About the Nitrite Cycle: Ammonia à Nitrite à Nitrate.

What Is The Nitrite Cycle?

In your fish’s natural habitat, it is surrounded by Nitrosomonas and Nitrospira bacteria that neutralizes toxic ammonia and nitrite. In the home aquarium, the water is initially clean and lack these bacteria. Usually, both bacteria colonies take about a week to colonize and begin establishing the tank. Ammonia ) is the initial by-product that will first be introduced to the aquarium through rotting food and fish and plant waste. It is very toxic to fish and in excess amounts, can burn their gills, reduce breathing and can be fatal if the condition isn’t improved. The nitrosomonas bacteria oxidizes the ammonia and converts it into less toxic nitrite (). From there, the Nitrospira bacteria that has colonized in the filter and gravel bed will oxidize the nitrite into much less toxic nitrate () and the cycle is complete. Nitrate is primarily removed during water-changes; which should be completed every two weeks to a month depending on bio-load (Lots of fish/overfeeding=more frequent water changes).

FAQ’s and Tips Before Getting Started:

Testing for Ammonia, Nitrite and Nitrate:

Ammonia will not be present in the tank until after the first week, especially in a “fishless” cycle (explained below). Wait until after the first week to test for Ammonia, ideal range is 5-20ppm. Nitrite will begin to develop during the 2nd and 3rd week of cycling, at this time the amount of ammonia should be lower than it previously was and nitrites should be developing. In the 3rd and 4th week, the bacteria should begin producing nitrate, and there should be yet another decrease in the amount of ammonia and nitrite, nitrates will begin to develop. If chemical spikes do occur, remedy it with a 15% water change. Products such as safe-start and stress-zyme (by API) can also help during spikes.

- Testing the tank water is important, excess levels of ammonia and nitrites can kill fish and the solution to such a problem is a 15% water change. A noticeable side effect to ammonia poisoning is gasping at the surface and “choking” or “coughing”.

- Testing water periodically and recording results is the best way to diagnose any fluctuations in the bacterium and toxicity of your aquarium.

Stock fish Gradually to Avoid an Ammonia Spike:

Even if nitrates are present and the cycle is initially complete, the bacteria will continue to grow at an exponential rate to support the amount of ammonia present in the tank. For this reason, it is better to add fish gradually, rather than all at once or in larger spurts to avoid overwhelming the current bacteria.

The Bacteria Both ‘Live’ in the Filter and Gravel Bed of the Aquarium.

Should I Hydro-Vacuum the gravel then?

- Yes, hydro-vacing the gravel while changing aquarium water is recommended because this will ensure that excess food, plant material, or ‘black matter’ (decomposed organic matter) is being removed from the tank. Take care not to hydro-vac too much of the gravel at one time though, as you ARE still removing some bacteria and removing too much could cause an imbalance ( > Bacteria). Only about 15-25% of aquarium water should be removed at one time to avoid such an imbalance, even in Nano and very small aquariums.

Where is the Bacteria located in my filter?

- All filters have some type of bacteria supporting component. Under-gravel filters use the gravel bed as its ‘bacteria holder’. Some hang-on-the-back mechanical filters include ‘bio-stones’. Some cannister filters contain ‘Bio-Balls’. Always be careful when cleaning your filter. Rinse these components in dechlorinated, room temperature water only if absolutely necessary.

o DON’T do a water change AND clean the filter at the same time.

Cloudy Water is Completely Normal

In the first 2 weeks of starting a tank, it’s actually a good sign. The cloudiness is a signal that bacteria is beginning to form and colonize.

- If cloudiness persists after 3 to 4 weeks, live bacteria or fish may be added.

- If cloudy water is also green, turn the tank lights off for 3 days straight. If problem persists or worsens, consider purchasing a phosphate remover filter media. This is usually a sign of a unicellular algae bloom caused by high light and phosphate concentrations.

Many beginner aquarists make the mistake of disregarding the Nitrite cycle when adding fish to their aquarium; either because they are unaware the process exists, or because they are so excited and can’t wait to add fish. This can cause MANY problems with the tank both immediately and months after initial start-up. The cycle can take between 2 and 4 weeks to complete, depending on the method of cycling.

The cycling process begins as soon as the tank is filled with water and organisms are added.

Method 1: “Fishless” Cycle

- Step 1: leave the tank filtering (with necessary equipment running) for 2-3 weeks.

- Step 2: Add 3 or 4 hardy starter fish and wait another week. (White clouds, Zebra Danio, Mollys)

- Step 3: Test water for Ammonia, Nitrite and Nitrate. At this time, if there are nitrates, then the tank is ready to be stocked. If there are no nitrates, add a couple more fish (optional) and wait a week or so.

- Step 4: Begin stocking the tank slowly, consider the maximum amount of fish you can have in the aquarium based on size (1In of fish per 1 Gal), and multiply that number by 1/8. Round up to the nearest whole number, that is the max. number of fish you could add at one time. Discretion is advised.

Fluval, Marineland, Tetra, API, and Doctor Tim’s all produce live bacteria supplements that can be added to the aquarium upon start up. These products jump start the number of live bacteria in the tank. Live bacteria products are always recommended and can shorten the cycling process by up to 2 weeks.

Method 2: “Fish-Included” Cycle

- Step 1: Add live bacteria by product dosing.

- Step 2: Leave the tank filtering (without fish) for 1 day to 1 week.

- Step 3: Add a few fish (of preference), See Step 4 of Method 1. Wait a week or so.

- Step 4: Test Ammonia, Nitrite, and Nitrate, if tests are showing 0-5ppm , , and than your tank is ready to begin gradual stocking. If tests are not ideal, hold off on stocking more fish for another week or so.

The fastest way to cycle a new aquarium is to introduce a pre-existing bacteria colony. This can be done by filling the new tank (up to 50%) with ‘old’ tank water or by replacing the new filter pads or bacterium holders (included with the filter) with ‘old’ filter cartridges from an established aquarium.

Method 3: “Transfer” Cycle

- Step 1: Fill tank with established water. Or replace new filter media with established media.

o Established water should also be clean water, let hydro-vacuumed particles settle or take water from the higher column of the established tank.

o Take note of any parasitic, bacterial, or fungal infections that have previously occurred in the established tank, as these can hitchhike with the water (and media, depending on the pest) and affect your fish later, its best to steer clear and start with a live bacteria supplement in this case.

- Step 2: Let pre-established water filter in the tank for approx. 1-2 weeks, testing periodically.

- Step 3: once nitrates begin to appear, gradual stocking can begin. See Step 4 of Method 1.

Why is the Nitrite Cycle So Important?

The goal of the nitrite cycle is to build a bacteria colony strong enough to accommodate the bio-load of the tank. The bio-load directly depends on the number of fish in the tank and the amount of organic matter present (over-feeding and decaying plants contribute to the bio-load). Moderate to high levels of ammonia and nitrite do not cause fish to contract disease, however it can cause stress, which weakens the immune system and can be a contributing factor to further issues. Water changes aid the bacteria in keeping levels under control in such a contained environment, however a semi-sustaining bacteria colony is necessary for keeping a happy, healthy aquarium.

I wrote this myself awhile back...hope its helpful some.

Mick Frost

It's nice to see someone actually mention Nitrospira, though they're much better at waste (Urea) conversion than they are at Nitrite conversion. Nitrobacter are usually the fastest to colonize for this purpose, especially in a fishless cycle.

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