Fishless cycle: ammonia source?

[AdamHorton]

Hi, I had posted a follow-up question in another thread about this but didn't get any response. Here's the thread: Cycling a tank with live rock: question I'll re-post the relevant stuff here:

I'm doing a fishless cycle in my 150G SW tank with 30G sump/refuge. I'm using 250lbs LR for my filtration. 2.5 weeks ago (Sunday, October 18; 19 days ago) I added the water to the tank and turned on the plumbing. I had spent the previous week soaking the LR in RO/DI water and trying to kill off everything that was on it previously. I added 4 raw shrimps to the tank to serve as the ammonia source.

Last weekend, after two weeks I had seen no readings of any kind: ammonia, nitrite, and nitrate were all zero. The shrimps I had put in looked pink but they had not even started to rot or decompose or anything. I put four more shrimp in but even now still zero on all readings and no sign of decomposing shrimp. I don't know why the cycle isn't starting...

I was thinking about stopping by the store and buying some pure ammonia to dose the tank with. I realize this is more difficult than using shrimps but maybe this will actually work? Is this the right course of action to take? How much ammonia should I dose?

[melosu58]

Are you sure your water test are working fine. Take it to your LFS and get them to check it out.

[husonfirst]

Four shrimp might not be enough in a tank with 180g capacity. I used ammonia when I cycled my new FW tank. I brought it up to 4 ppm initially and was completely cycled in 15 days.

Fishless Cycling

[AdamHorton]

I will get ammonia and start dosing the tank with that today. When I get a chance I'll take a water sample to the LFS to get it tested. Thanks for the help, and for the article link.

[AdamHorton]

Turns out my tests are working correctly...

I started adding ammonia to the tank on Saturday, and that seems to have kick-started everything:

Adam's FLog: Kicking the cycle in the butt

The shrimp that were in there have also started to decompose pretty rapidly, almost like some bacteria were in there eating them or something

[AdamHorton]

Two sets of measurements since then. I added the first ammonia Saturday night, 40mL of solution that night and 20mL of solution every night since then. I measure right before I add more ammonia, so the measurements reflect what the bacteria in the tank can do in 24 hours starting from 2-4 ppm ammonia:

Sunday:
1.5 ppm ammonia

Monday:
0.25 ppm ammonia
0.5 ppm nitrite

Tuesday:
0 ppm ammonia
0.5 ppm nitrite

Wednesday:
0 ppm ammonia
0.1 ppm nitrite
10 ppm nitrate

...wow, this is going really fast. I knew the first part before the nitrite spike was supposed to fly by using this method, but it took no more than three days for the nitrites to start coming down. This is really exciting, but nothing good in SW ever happens quickly so I'm wondering what's about to explode here...

I plan to wait at least 1-2 weeks after my first zero readings for ammonia and nitrite until I add a CUC, and of course I will do a whole bunch of water changes to get the nitrates down.

I assume I should continue to dose 20 mL/day of ammonia solution until I add livestock? Also, I eventually want to have chaeto algae in my refugium. When would be a good time to add that? Should I wait until after the water changes to get the nitrates down or would the increased nitrate levels actually help the algae along? I don't know much about keeping chaeto -- maybe that's a question for a different thread.