Tips and Tricks For Your Fastest Fishless Cycle!

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Help to get through the boring part of keeping tanks.

This article was contributed by Aquariums Advice member 7Enigma

Before reading this article you should familiarize yourself with the Nitrogen Cycle.

There always seems to be a large number of posts in this forum about fishless cycling, and I wanted to put this article together to help folks get through this rather boring period of time between starting up a tank and introducing your fish/inverts. My intent with this article is to reduce the cycle time as much as possible; while giving the science behind why a particular step is taken. Frequently in this hobby we are told to do something without understanding the underlying reason and that is not a good thing. This is why so many people get discouraged with this hobby and leave. Please note: I feel fishless cycling is the ONLY way a tank should be prepared for fish.

Let’s go over the basics very quickly as I’m sure most of you have read this over and over:

The purpose of cycling is to build up the beneficial bacteria in a tank that feed off the waste materials of your fish/inverts. Without these present in great enough numbers, your fish will kill themselves with their own waste. By building up these bacteria prior to adding in fish, you avoid harming your fish. Unlike traditional cycling where a small amount of hearty fish are introduced into a tank, and slowly additional fish are added, fishless cycling (when properly performed) allows for a complete stocking of the tank at once. This is a huge benefit, and one which is often overlooked.

The 2 types of bacteria we are looking to grow convert ammonia (fish waste which is quite toxic) to nitrIte (actually more toxic than ammonia but not as long term damaging), and finally to nitrAte (relatively non-toxic unless allowed to build up to large amounts). So that’s:


The first conversion to nitrIte occurs faster than the second conversion to nitrAte. Once the cycle is completed PWC’s are required to keep the nitrAte level acceptable (general consensus is <40ppm) unless plants are present.

OK, now that all the boring stuff is out of the way lets get to speeding up your fishless cycle!

If you have a completely new tank, these are the steps you want to do in the order they should be done for the most "bang for your buck":

-Setup the tank, put all filters/heaters/decorations/etc in place. Fill your tank up with tap water. DO NOT USE A DECHLORINATOR AT THIS TIME!

-Turn everything on and make sure it all works. Better to find out now that the heater is broken, then 2 weeks into the cycle when nothing is happening

-Let the tank run for 30 minutes or so and check for leaks/malfunctions

-Now add in your dechlorinator (I prefer Prime). Waiting to use a dechlorinator essentially sterilizes your tank from any contaminants (especially if you have chloramines in your tap water).

-Purchase a good liquid reagent test kit that tests ammonia, nitrIte, nitrAte, pH, etc. A lot of us on here use the Aquarium Pharmaceuticals FreshWater Master Test Kit (AP test kit for short).

-Now you need an ammonia source! Many fishkeeper's forget this step and without food, the bacteria will not multiply. Pure ammonia is the easiest and best way to do a fishless cycle however, you can use fish food or a raw shrimp but measurements will not be as accurate. You need to find pure ammonia that does not contain any additives such as detergents or scents.

-With the ammonia purchased, and your test kit handy, dose the tank to ~5ppm ammonia. If you add too much, do a Partial water change to reduce the level, if you add too little, dose more. It doesn't need to be exact, but just aim for 3-5ppm. Every couple of days test the ammonia level, when it gets below 1ppm, add more ammonia to keep the level above 1ppm. Normally when I see it get below 1ppm, I dose 3-4ppm back in. Never let it go to zero (until the cycle is finished) or you risk killing off your ammonia to nitrIte bacteria!

-Turn your heater up! Aim for 85-87F. This increased temperature speeds up the metabolism of the bacteria which reduces the cycle time.

-Turn on any bubble wands, lower the water an inch or two if using HOB filters, turn on any PH's you might have. Increasing agitation increases the dissolved O2 levels which bacteria like/want/need.

-Buy/borrow a small bottle of pH down. Add 1-2 drops per 4 gallons of tank water. These pH products contain large amounts of phosphates which your bacteria need to grow. This small amount will not affect the pH of the tank and will supply all the phosphate needed. Lots of "my cycle stopped/stalled" posts can be attributed to phosphate deficiency. A small amount of fishfood can probably also be substituted in place of this.

-Add in a VERY small amount of flake fish food. When I mean small I mean microscopic! About the size of a grain or 2 of rice. Pulverize it into a very fine powder and add it in. This will take care of any trace elements required by the bacteria and probably the phosphate requirement as well.

-Now its time to seed the tank! This is the single most important step in the entire cycle. The more seed material you can procure, the faster the cycle will go. Seed material is anything you can take from an established tank. Filter media (sponges/floss/ceramic media) is the #1 best. This stuff is FULL of bacteria and exactly what you want. Next up would be substrate (sand/gravel). And last but not least would be decorations/ornaments. Do you have a friend with a gaudy/hideous pink castle that's been in his goldfish tank for 3 years? Beg/plead/steal it from him/her for a couple of weeks. But make sure you keep anything wet in the tank water until you can add it to your tank If it dries out in transit, the bacteria's dead!

With your tank setup and seed material you now want to maximize colonization of the surfaces. If you are given a piece of filter media squish it in the tank water first. This will cloud the tank with bacteria laden particles. These will fly all over the tank and "seed" the surfaces with bacteria. Then put the filter material in your filter. It doesn't matter if it's not made to fit, find a way to get it in there. HOB and canister filters normally allow for several compartments, make one of them the seed filter material. Place it at the FRONT of the filtering. By that I mean put the seed material as the first thing the water hits when entering the filter. This will cause any bacteria that is released from the seed material to contact the new filter first, which is where you want the bacteria to be.

If you are given substrate (and don't mind it in the tank) spread it out all over the bottom. This maximizes surface area and will allow the most contact with the bacteria and food source.

If the substrate is something you don't want in the tank after the cycle put it in the foot of a new UNWASHED piece of pantyhose. Rinse the pantyhose under tap water but make sure it never went in the wash. Detergents/fabric softener will kill your tank! Squish the substrate around every day or two. You'll notice it will cloud the tank. This is a good thing as bacteria is being released into the water. This is how I cycled my 20 gallon. I did not have filter media, only a small amount of gravel from an established tank. I put 1/2 the gravel in a filter insert in my HOB, and the rest in some pantyhose (since I had PFS and didn't want the gravel). A couple of weeks after the cycle finished I removed the seed gravel (you don't want to remove it too soon or you may cause a minicycle).

Now for a note about bacteria. They are surface adherers. That is, very little of the bacteria is present in the water itself, the majority is attached to the surfaces in the tank. This means that a PWC during the cycle is not necessarily a bad thing. It's normally not needed, but if it is for some reason (say you overdose on the ammonia), don't fret!

A quick word on pH. Ideally you want the pH of the tank to be ~7.5. The ammonia to nitrIte bacteria prefer a higher pH (closer to 8.0), while the nitrIte to nitrAte bacteria prefer a lower pH (closer to 7.3). Go too high and your nitrItes will build up, go too low and your ammonia won't get converted. If you have a pH crash (either too high or too low, say pH 6.0 or pH 9.0) you have to do a PWC. At these ranges your bacteria will seriously begin to slow down metabolism.

Keep the tank lights off and direct/indirect sunlight to a minimum. This time in the tank is RIPE for algae outbreaks. High ammonia levels, steady CO2 levels (from high aeration), and possible light can cause your tank to look like pea soup. The bacteria do NOT require a light source, and in fact, direct sunlight can cause the bacteria to multiply slower. Bottom line, keep it dark!

So now you have the perfect temperature, a steady food source with trace elements in abundence, good oxygen levels, your all set!

When you see your ammonia level drop to below 1ppm, increase it back up to 3-5ppm. You will most likely build up a LARGE amount of nitrIte because the bacteria that convert nitrIte to nitrAte were at a disadvantage waiting for their food (nitrIte). I've often thought of creating a product of pure nitrIte for cycling. That way you can dose both ammonia and nitrIte at the beginning which would speed up the entire cycle. Now don't go and steal my idea!

Watch your nitrAte levels. When they start to rise wait about 5-7days and, if your nitrIte levels are really high (>10ppm), I’d recommend a large PWC to bring the number down into a readable range. This will not affect the cycle, and will keep you sane as you can watch the levels vary. You might see the levels continue to go up as you will still have more ammonia converting bacteria, but if you watch the nitrAtes you’ll know your heading in the right direction. Several members on here have really been done the cycle, but because there was so much nitrIte in the tank they didn’t know it! (hint I was one of them….)

Once you can convert 1-2ppm ammonia completely to nitrAte in 24hours or less you can do a large (or several) large PWC’s to get the nitrAtes below 40ppm (<20ppm preferably). Now decrease the tank temperature to 78-82F if housing tropicals, otherwise whatever temperature you need. Make sure the temp is stable before addition of fish.

Now your all set to fully or near fully stock your tank!

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