Fishless Cycling Question

[Squibbles]

I have a new 240ish gallon frag setup I'm currently cycling. Its been 3 weeks and I'm curious as to whether or not I need to do a water change to get the nitrate and nitrate numbers down.

It seems to consume the ammonium chloride I've been dosing and ammonia levels are 0 every morning before redosing 1PPM, however nitrites are still over 5PPM and nitrates have crept up to almost 100PPM.

Are the current nitrite and nitrate levels slowing the nitrite to nitrate conversion, or am I having the nitrifying and denitrifying bacteria fighting keeping nitrates high? (I currently have 40lbs of siporax media in the sump set up in a "denitrifying" block before the return)

Any tips would be appreciated.

 

[Tahoe61]

Do not add any more ammonia, at 3 weeks in your numbers look good. Let the nitrite fall to 0/undetectable, give it a couple more days and see where the nitrate value ends up.

Nitrates are high imo because you have continued to add ammonium chloride, you can stop that now.

If after 5 days with no ammonia dosing and you continue to see a detectable nitrite and higher nitrate levels then yes I would proceed with a water change.

 

[Squibbles]

Sounds good. This is the first time I've cycled a tank without "Live Rock" and damsels. Figured I should be a responsible reefkeeper and do it the humane way.

Thanks for the input. I'll shelve the ammonium chloride for the next time I need to cycle!

 

[Tahoe61]

Excellent you went the fishless cycle.

 

[Randy Holmes-Farley Verified Community Expert]

I would also suggest that if nitrite is really that high, nitrate may not really be that high. With some kits (like Salifert) some nitrite shows as a lot of nitrate.

In any case, I'd normally consider a big change on a small tank, but in a big one like yours, it might make more sense to deal with the nitrate in other (less expensive and time-consuming) ways (such as organic carbon dosing).

 

[Squibbles]

I would also suggest that if nitrite is really that high, nitrate may not really be that high. With some kits (like Salifert) some nitrite shows as a lot of nitrate.

In any case, I'd normally consider a big change on a small tank, but in a big one like yours, it might make more sense to deal with the nitrate in other (less expensive and time-consuming) ways (such as organic carbon dosing).

Since there are no fish in the system, is there a limit to the carbon dosing that you'd recommend?

 

[Randy Holmes-Farley Verified Community Expert]

Since there are no fish in the system, is there a limit to the carbon dosing that you'd recommend?

If you have a good skimmer on the tank, I'd dose vodka or vinegar reasonably aggressively, but beware of cyano since some species may be able to consume organics.

If you use vinegar, maybe 20 mL per day for a week, then twice that and see what happens by the end of the second week.

The nitrate drop may become phosphate limited. So you might need to dose a little of that as well.

 

[Squibbles]

Let the dosing and agressive skimming begin!

 

[Randy Holmes-Farley Verified Community Expert]

If it seems too complicated, you can always go the water change route.

 

[Squibbles]

If it seems too complicated, you can always go the water change route.

I think I'll try the dosing method first. water change would be an entire bucket of salt. lol

 

[Randy Holmes-Farley Verified Community Expert]

What kind of rock is it?
Some comes with its own load of phosphate.
That may determine if phosphate will become limiting or not to nitrate reduction.

 

[Squibbles]

There is a small amount of muriatic acid washed live rock that I've had sitting around in the garage that did not fit in my display systems. Using that as well as 40lbs of Siporax media in the sump (I believe that it is sintered glass).

I would have used some of my display live rock to speed the cycling, but I had some vermetid snails that I wanted to keep out of my frag system so I can eventually reboot my display tanks.

I'm going to need to dose phosphates I think.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, I think it likely then, but you can control it fairly easily if you can test for it effectively.