Cycling/Water Change Question

Joshua Jordan · Sep 13, 2017

I am on my third week of cycling my new 32g LED Biocube. I started with 28lbs of Arag-Alive sand, 25lbs of mostly dry-reef rock. (I actually needed about 8 lbs of rock to finish the scape and that was Live Rock from my LFS).

I started the cycle using the shrimp method, where I put a dead-cooked shrimp from the grocery store in the tank and let it sit for about a week. My ammonia, of course, spiked. Next, my nitrites and then my nitrates. All I ran filter-wise during this time, was a piece of filter floss. I did water testing regularly and saw that the ammonia levels had gone back down to zero, but my nitrites and nitrates were still pretty high. It was at this time that I removed the shrimp. Now, two and a half weeks later, the nitrites are down to zero and the nitrates are getting really low. (25ppm and still dropping)

I have gone ahead and installed my InTank Media Basket with Purigen and Chemi-Pure Elite. (My protein skimmer will be in tomorrow) My questions is this:

I have always read that you are supposed to do a 10-20% water change after your tank is done cycling to get rid of the remaining nitrates. However, do I still need to do a water change if it looks like my nitrates are at a good level?

I'm almost nervous that I didn't leave that dead shrimp in there long enough. (one week) Do you all think that my tank is cycled if my ammonia tested super-high, and has now gone back down to zero, and the same for my nitrites and now it looks like that is where my nitrates are heading too?

I just want to make sure that I don't add anything to the tank too soon.

Thoughts?

Mal11224 · Sep 13, 2017

Welcome to reefing and R2R. If you nitrogen cycle started then I would say that you have cycled your tank. 1 week is long enough for the shrimp to be in there. As long as your ammonia and nitrites are undetectable leaving you with nitrates in your system then you should be good. Also, water change is a must after the cycle. About 40%, then a week later, you should do a smaller water change. During this process, make sure that you levels are where they need to be and then you should be able to add a fish to your tank and observe how it is doing before additional livestock is added. Patience is key. You can add a clean up crew to your tank now if you had plans.

beaslbob · Sep 13, 2017

If you had started the tank with macro algae (in a refugium) it very well could have registered no ammonia with a small initial nitrate spike. Then about 3-4 weeks later the nitrates would drop down.

Macro algae consumes ammonia first then nitrates for it's nitrogen.

The use of water changes to lower nitrates is only necessary when those nitrates are not being consumed by things like macro alage.

my .02

glb · Sep 14, 2017

Are your nitrates falling on their own? My concern is that they need a food source to keep multiplying. I'd recommend dosing with ammonia up to 2ppm and waiting to see if it goes back to zero in 24 hours. Good luck'

Jason mack · Sep 14, 2017

glb said:
Are your nitrates falling on their own? My concern is that they need a food source to keep multiplying. I'd recommend dosing with ammonia up to 2ppm and waiting to see if it goes back to zero in 24 hours. Good luck'

+1 for this advice ..