Nitrate post cycling

[Shilpan]

Hello I'm a little confused about cycling. I was told I might need to do a 20% water change post cycling to lower nitrates. (NB still setting up tank have not started cycling).

But don't nitrates need to be very low, almost 0, in a saltwater system? Won't nitrates be very high following a cycle because there was no way for the nitrate to escape? So why don't we need to do a 100% water change always after cycling? I don't see how else we deal with this high level of nitrate post cycle...

My LFS person said your ammonia, nitrites should be 0, but nitrates should also be 0 or close to it, if not your tank isn't cycled. But how do we get rid of this nitrate without a 100% water change??

 

[bang guy]

Nitrates do not have to be zero.

For some delicate corals is should be below 10ppm but for most animals it can be significantly higher. Think of Nitrite and Nitrate as saltwater smog. If there's a lot of it then it's probably uncomfortable so you do need to monitor and keep it low if possible but it's not going to start killing things at low levels.

 

[Shilpan]

So how do we keep it below 10ppm during cycling? What's stopping it from building up to above 10ppm if I'm ghost feeding every day?

Sorry I'm just a bit confused. I see a lot of nitrates at the end of the cycle and I don't know why we don't have to do a 100% water change because how else do they leave?

Thank you so much this is probably a dumb question...

 

[bang guy]

Algae consumes Nitrate, bacteria deep in live rock consumes Nitrate.

You have no delicate corals so don't worry about it being above 10ppm. Once the algae, such as Coralline, begins to grow nitrate will begin to fall.

Remind me, do you have a sump? Were you planning an algae refugium?

 

[florida joe]

Just my .02 do some research on denitrification. But in a nut shell. There are two basic ways we lower nitrates in our tanks. One is Denitrification. In this method nitrate is used as a biochemical by anaerobic bacteria. The second is assimilatory nitrate reducing. This is when the nitrates are absorbed by algae. And then we farm the algae. Usually when we talk about nitrate lowering it’s through the anaerobic method. NOW if we do a 100% water change we are out competing the anaerobic bacteria for food to grow. You can certainly continue to do 100% water changes but you will never attain a constant natural nitrification and denitrification cycle.

BTW sorry Bang you know me and telling hobbyists to do their research

 

[Shilpan]

Hey guys!
Ok yup I know what you're talking about! I didn't realize that the rockwork and sand bed were sufficient to provide enough habitat for anaerobic bacteria. Yes I have a sump! And there are bio balls in there at the moment which I should remove right?

Should I put a deep sand bed in my sump (I assume deep sand beds will create anaerobic zones)? Or make a refugium? Or put live rock there? Or can I put all 3? That would be so cool to have complete nitrogen cycle and export it out of there too as N2.

 

[florida joe]

All of my suggestions are IMO. A deep sand bed is not needed in your sump for denitrification as long as you have sufficient porous rocks in your tank. As far as a refugium remember its original purpose was a place of refuge. A place to grow copepods, macro algae EST. As for the bio balls and should you remove them or not, that has been discussed on this site ad nauseum. I have had the same bio balls in my wet dry sump since its inception. That was in 2000

 

[Shilpan]

Ahh ok thank you!

I think I'll put dry rock in there during the cycling curing process to create more porous rock habitat for bacteria. If I find nitrates are unmanageable later then I can add a refugium. I have learnt after 3 years of freshwater fish keeping not to feed too much and control my nitrates that way. I hope I can do the same for this system.