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just a couple of lines i promised i would write


Staff member
Following on from a post in site feedback and suggestions I didn't know where to post this,, so I've plonked it here

comments and possible changes welcome guys and galls :-d

Methods for cycling a marine aquarium
Ok, so you have your new marine aquarium all set up and ready to go, whether you have used live rock, dead rock, reef bones or artificial rock the various methods used are designed to meet the same end result. Making your aquarium safe for its future inhabitants. Unlike an aquarium that has been set up and running for some time where the main science to keep it running successfully is chemistry, an understanding of the biology of your aquarium is also helpful when it comes to you cycling your new tank.
To understand when your tank is cycled and safe for its inhabitants its useful to know what we’re aiming to achieve and what method may be best to use.
The three main accepted ways are, The fish in cycle. The addition of ammonia, and more recently the Instant cycle in a bottle method.
For all three methods it’s important to have a marine Ammonia (NH3) Nitrite (NO2) and a Nitrate(NO3) test kit.
Our ultimate goal is to cultivate three types of bacteria within the substrate and rock in the aquarium, these are essential to the wellbeing of the tanks inhabitants, the first of these types ‘Nitrosomonas bacteria’ use ammonia and oxygen to survive and in the process excrete nitrite which in turn is used By a bacteria called ‘Nitrobacter’ which in turn with the use of oxygen excrete the chemical Nitrate, the Nitrate is used by bacteria that live in the anoxic areas of your tank, (low oxygen), notably deep within live rock and within the lower levels of the substrate and convert the nitrate into nitrogen gas which harmlessly escapes the aquarium through the water surface.
You can think of these three chemicals as a set of traffic lights. Ammonia RED, extremely toxic to fish and invertebrates, Nitrite, AMBER, not as toxic as Ammonia but still dangerous even in low concentrations and NITRATE, less toxic than both Ammonia and Nitrite but can be dangerous if left unchecked at high levels for prolonged periods of time.
The Biological removal of these chemicals from within the aquarium is commonly known as the nitrogen cycle.
Ammonia- converted to Nitrite-Nitrite converted to Nitrate-Nitrate converted to Nitrogen gas.
The inhabitants of your tank are constantly producing ammonia so it’s worth remembering once you have completed the initial first cycle of your tank, it is in a constant state of cycle with the bacteria removing these unwanted chemicals as fast as they are being produced, once your tank has reached this stage it is known as a biologically balanced system and with good husbandry it can remain balanced indefinitely.
So let’s look at the most common ways of achieving this, how to monitor its progress and which way may be best for your system.
This is a way that has been used since the beginning of fish keeping, one or two hardy fish are added to the aquarium to kick start the cycle by producing their own ammonia and be hardy enough to withstand the initial ammonia and nitrate spikes until there is enough bacteria to cope with their waste and the aquarium water becomes safe. Often these fish would die and more would be added until eventually they survive and the nitrogen cycle is completed.
Fortunately, modern and safe methods of the fish in cycle have been developed and this can now be a safe and efficient method of cycling a tank with few or no drawbacks.
To do this you need to test the water of your newly filled tank for signs of ammonia, nitrite and nitrate, its useful to make a note of your test readings, then wait 24hrs and test again, note the changes, wait 24hrs and test again, again take note of the changes. Keep doing this until you see changes in the readings you are getting, ideally you want to see an ammonia reading which will then fall, nitrite rise and then fall followed by a rising of nitrate.
If this is what you see, then when ammonia and nitrite have been at zero for three of four days and assuming Nitrates are not too high (20-30 ppm or less) it can be assumed that the tank is safe for its first inhabitants. Nowadays rather than adding fish its best to add some clean-up crew (CUC) such as snails and hermit crabs, (you’re going to need them for the up and coming algae blooms, Diatoms, Hair algae and possibly Cyanobacteria.) test the water regularly for the next two or three weeks, it’s also a good time to start with your water change regime. you should also start to see a weekly drop in nitrates. Once you see this and ammonia and nitrite have remained (0) your tank is now safe to slowly start to add fish.
The culturing of beneficial bacteria in balance to the tank inhabitants without the risk of excessive nitrates and phosphates therefore reducing the inevitable algae blooms to a minimum.
Especially good for large tanks, 250 litres and above due to the buffering and dilution of fish waste by the volume of water while the bacteria count catches up.
Can be a quick method of cycling if good quality reef ready rock and substrate is used.
Can be sometimes difficult to see if the cycle has completed.
Not good for small tanks where the levels of NH4, NO3, can rise suddenly.

Cycling by the addition of ammonia is commonly used by freshwater fish keepers but can be equally useful to the marine aquarist, it involves adding measured amounts of pure household ammonia to the water to force the growth of ‘Nitrosomonas’ and ‘Nitrobacter’ bacteria , it’s important to use unscented ammonia, normally found in supermarkets as ammonium hydroxide or aqueous ammonia (the ingredients on the bottle should read only ammonia and water) some household ammonia contain a binding agent, (this is fine) a good although unscientific test whether your bottle of ammonia safe to use is to shake the bottle and remove the cap, if its foamy then it likely contains Dyes or scents, (You don’t want this) if not your good to use.
First you need to know how much ammonia to add to your tank to start the cycle underway. The amount of ammonia in your bottle can vary from 5% to 15% free ammonia so a good idea is to test using a syringe and a litre of water and see how much ammonia in mL it takes to raise the level in one litre of water to 4 or 5ppm (parts per million) or an easy to read colour on your test kit. Do some maths and once you have determined how many mL it takes to ideally bring your tank water to around 1ppm its time to test each day to see the cycle complete, once the ammonia has dropped to (0) you should see the nitrite continue climbing and then drop to (0) if you wish although not necessary you can repeat the ammonia dose until you see the level of ammonia and nitrite drop to (0) in less than a 12hr period. Although it’s worth mentioning the more ammonia you add the higher the resulting nitrate reading will be so it’s worth being cautious and some reasonable water changes may be needed after the cycle is complete, ideally nitrates want to be at 20ppm or lower before the addition of CUC and noticeably falling before the addition of fish.
unlike the freshwater guys who go for 4 or 5ppm and hold it there for a prolonged period in order that when adding fish they can fully stock in one go and rely on a very large water change, or changes once the cycle is complete to reduce nitrates this is not recommended for the marine aquarium
Easy to see and be confident the cycle has completed.
Good method for smaller tanks where water changes to remove excess nitrates don’t prove too expensive
Produces an unbalanced bacteria count leading to die off of bacteria prolonging the cycle
Possibility of raising nitrate levels leading to more initial water changes and prolonged algae outbreaks.
Another common method of producing the ammonia to cycle your tank is to add an ammonia source in the way of a raw prawn (yes from the supermarket) and allow it to decompose and in turn release ammonia which can be measured to see the cycle run its course. This has an obvious scientific problem, add a tiny shrimp to 500litres of water and the chances are you won’t be able to measure any rise in ammonia and as such adding a large lobster from the fishmonger to 100litres of water would probably take years for the cycle to complete so an amount of common sense is needed. In general, one small prawn per 100litres of water will produce enough ammonia to be measured effectively to see the cycle at work.
If done correctly a reasonable balance of bacteria can be achieved with little excess bacterial die off.
Good for large and small tanks alike.
Can take a long time to fully complete the Nitrogen cycle due to the time taken for the prawn/prawns to fully decompose.
Either way whichever method you use to cycle your new tank and you are confident it’s fully cycled once you start to stock it with fish you need to stock slowly and sensibly, each time you add a fish your effectively adding additional Ammonia, Nitrite, and Nitrate to the water and you need to allow time for the bacteria count to catch up to deal with this increase.