To see the results of this cycle follow this link>>> but read the below for the process.

So, after much deliberation, I decided to cycle my tank with a prawn. I had originally started with ghost feeding, but I could never see where the flakes had gone and truthfully I wasn’t sure how much to add, so I figured I could just pop a raw prawn in the tank and forget about it until the cycle was done.

Some things you should know about cycling your tank with a prawn:

  • It stinks! I mean really stinks once it starts to rot.
  • Put the prawn in a bag, this will save you trying to track down lumps of rotten fish in your tank
  • It’s slow… and I can’t stress that one enough.
  • It’s super easy!

I am going to assume you know about the basics of the cycle, I am not going to sit here and teach Grandma how to suck eggs. If you don’t the google the nitrogen cycle in a fish tank, there are far more qualified people than me to explain that to you!

All Pond Solutions High Grade Activated Carbon AC-500
All Pond Solutions High Grade Activated Carbon AC-500

Now, back to my prawn. So, yeah, the little sucker stank the house out after a couple of days. Thankfully I had my trusty bag of activated carbon on hand which once that was put back into the tank, sorted the smell out within a day or so. So top tip, if you’re cycling with something rotting, make sure you have carbon on hand to deal with the stench.

If you add carbon, just be aware you will need to remove it and you may have another mini-cycle as the bacteria may colonise in your carbon rather than just on the rock where you want it.

By putting the prawn in a bag, it means that when it is time to remove him or her from the tank, I can just remove the bag and I don’t have to go hunting around my tank for lumps of the remains. So there is another top tip, make sure you have a back or filter sock on hand to hold it in.

SLOW. SLOW. SLOW. That is what this cycle is all about. The prawn takes a couple of days to get really ripe, then it will start producing ammonia. It will leach it out slowly into your water and your cycle will begin.

Microbe-Lift Gel Filter Starter
Microbe-Lift Gel Filter Starter

Establishing a reef tank is all about time, everything takes time! The longer it takes, the better it will be in the long run. There are many successful tanks that have used bacteria bought in a bottle, but the majority of the really stunning, long-established tanks have started things slowly and let nature take it’s course when it comes to establishing bacteria colonies.

I personally, bought some filter starter (there is a review of the one I chose in the marine section of this site) and I am letting the rest take as long as it needs. To be honest, I wish I hadn’t even bought the filter starter, I wish I had done it all with just the shrimp but impatience got the better of me.

How about a Q & A section?

Q: How much of a prawn do I use?

A: There is no right answer to this. If you have a small tank I would say one-third of a prawn would be plenty. For a medium sized tank consider half of a prawn and for large tanks a whole prawn. There shouldn’t be any need for multiple prawns.

Q: Should I put the prawn in whole?

A: You can do, but the prawn will start to break down quicker if it in smaller lumps.

Q: What should I put the prawn in?

A: You can use a little mesh/filter bag to keep the prawn in one place. It will save you from having to pick out the chunks when your cycle is finished.

Q: How long should I leave the prawn in my tank?

A: Leave it in your tank until you add your first fish. Do not add your first fish until your cycle is complete and your water parameters are right!

Q: How long will the cycle take?

A: This depends on a variety of factors. Was your filter media new or from an established tank? How much live rock do you have? Did you use live rock or dry rock? There are so many variables that the only sensible answer to that question is 2 – 8 weeks. Just got to wait it out I’m afraid!

Prawn to start the Nitrogen Cycle
Prawn to start the Nitrogen Cycle

The beauty of this method is that it is just a case of pop the prawn in the tank and forget about it. You don’t need to remember to feed the tank, you don’t have to worry about a build-up of rotten food and you know once your parameters are OK, your tank has enough bacteria to sensibly support life.

But, make sure you do your water tests throughout your cycle. Not only will it help you to learn about your cycle, but it will show you when your parameters have spiked, then dropped, then subsequently that your tank is ready! Remember, you’re not keeping fish, you’re keeping water suitable for fish!


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