Is it even possible to have an Uncycled SW tank?

[MooseMama]

I'm preparing a series of lessons on basic fish husbandry, particularly since several of my students have asked about taking home and keeping some of the surviving baby platies.


My intention is not to go into much detail about SW aquariums, but just to explain the basic differences between SW and FW. With FW I will be going into more details, both for how to properly set up and care for cycled and uncycled.


I know the question will come up, so can anyone tell me, is it even possible to have an uncycled SW aquarium, not simply a temporary quarantine tank, but to actually keep fish permanently in an uncycled set-up?

 

[Aiken Drum]

If there is fish and fish waste in a tank then it will cycle. The exception might be that in a tank with very low pH and carbonate hardness (KH) the microbes normally responsible for the nitrogen cycle stop functioning because they need the carbon in the KH. In low pH the ammonia is mostly going to be non-toxic ammonium so it doesnt matter if the tank isnt cycled. But even there, low pH/ KH tanks will still cycle. We are discovering more about the nitrogen cycle all the time, and denitrifying microbes are being discovered that arent tied to pH and KH and get their carbon from CO2 which will be abundant in low pH water. People keep discus in low pH water where the common denitrifying microbes wont function, but their tanks will still cycle as these different microbes grow.

Saltwater isnt low pH/ KH though. Its chock full of disolved minerals and has high pH. The high pH makes the ammonia mostly toxic free ammonia, so an uncycled Saltwater aquarium is going to be far more hazardous than most uncycled freshwater aquariums. But given time, an uncycled saltwater aquarium will become a cycled saltwater aquarium. Its a natural process that just happens given time.

 

[Andy Sager]

I'm preparing a series of lessons on basic fish husbandry, particularly since several of my students have asked about taking home and keeping some of the surviving baby platies.


My intention is not to go into much detail about SW aquariums, but just to explain the basic differences between SW and FW. With FW I will be going into more details, both for how to properly set up and care for cycled and uncycled.


I know the question will come up, so can anyone tell me, is it even possible to have an uncycled SW aquarium, not simply a temporary quarantine tank, but to actually keep fish permanently in an uncycled set-up?

Yes it's possible but would require 100% water changes daily or every second day. Anytime there is any amount of ammonia (created from the fish) present, the " cycling" ( the creation of a biological filter bed) process will begin.
In Freshwater, it's very possible because when the Ph of the water reaches lower than 6.0, nitrification is inhibited. Below 5.0(?) it stops. The good news is that lower than 6.8, toxic ammonia is converted into non toxic ammonium. ( In reality, up until a Ph of 11, there is a mixture of ammonia and ammonium but the higher the Ph is, the more toxic the ammonia part becomes. For our use in aquariums, keeping a Ph less than 6.8 serves our purposes. ) In Marine tanks, the Ph MUST be over 8.0 for the fish to stay healthy so there is no way to stop nitrification unless the ammonia is removed.