Why is my tank re-cycling

[good11s]

OK help me out. My tank has been set up for about two months and Fallow. I cycled the tank with a raw shrimp from the store. The tank was going great with lots of pod growth

Last week my parameters were solid: NH3=0, NO2=0, NO3=5-10ppm, PO=0. Then all of a sudden last night I have a NH3 spike and my NO3 are 0. What the heck?

The only thing that has changed was I added new PC bulbs. I have a pretty good datom bloom in my fuge and even in the tank, and some good alge growth on my rocks. I can figure out what is happening.

I am concerned since I have inverts arriving tomorrow.

TANK MAKEUP
75 gallon with 130lb LR. 3-4" (80lb+) LS.
40G sump with LR rubble, and fuge with Cheato and a DSB.

Thoughts?

 

[Kurt_Nelson]

OK help me out. My tank has been set up for about two months and Fallow. I cycled the tank with a raw shrimp from the store. The tank was going great with lots of pod growth

Last week my parameters were solid: NH3=0, NO2=0, NO3=5-10ppm, PO=0. Then all of a sudden last night I have a NH3 spike and my NO3 are 0. What the heck?

The only thing that has changed was I added new PC bulbs. I have a pretty good datom bloom in my fuge and even in the tank, and some good alge growth on my rocks. I can figure out what is happening.

I am concerned since I have inverts arriving tomorrow.

TANK MAKEUP
75 gallon with 130lb LR. 3-4" (80lb+) LS.
40G sump with LR rubble, and fuge with Cheato and a DSB.

Thoughts?

Were you "feeding" your tank while it was fallow? In other words, were you supplying it with an ammonia source such as fish food, etc?

The original cycle established the beneficial bacteria, but for them to survive they need a source of ammonia. Normally, this is supplied by fish waste, respiration, excess food, etc. But in a fallow tank, you need to somehow get them the ammonia they need.

If you weren't feeding the tank, you could be seeing a die off of the bacteria. I believe it was in Fenner's book that he mentions that folks would be surprised at the bioload from just their bacteria, and that a bacterial die off can foul a tank just as much as a critter dieing.

The nitrates going to zero from 5-10 could also be your semi-deep sand bed doing its job of converting nitrates to nitrogen gas.

 

[good11s]

how often should I be feeding a fallow tank? daily? weekly?

 

[cmor1701d]

What Kurt said!

 

[melosu58]

I would put a few flakes in there every week. But yes that could be it if the tank was not fed every once in a while.

 

[good11s]

I had put a little brine shrimp in once but it was probably not enough. SHeesh, it has only been a few days since the raw shrimp finally disappeared.

Any thoughts on how to handle the inverts I am getting tomorrow? I ordered a "kit" from Saltwaterfish.com, they should be on my doorstep tomorrow.

 

[melosu58]

Yes some frequent PWC`s will have to be done to keep the ammonia and nitrites down. Inverts dont do good with that combination.

 

[Kurt_Nelson]

I had put a little brine shrimp in once but it was probably not enough. SHeesh, it has only been a few days since the raw shrimp finally disappeared.

How long since your cycle ended? From your first post, I guess I assumed your tank had been cycled for 2 months and been fishless. If it's only been a few days since your nitrItes disappeared, then you shouldn't be seeing a bacterial die off. If it's been a few weeks, then that's probably it. Either way, with nothing else in the tank (unless it's something big that's stuck in your rock somewhere that hitchiked in) to decompose, I'm not sure where else the ammonia could be coming from. Unless you went on a cleaning binge and got a bunch of Windex overspray in your tank.

Any thoughts on how to handle the inverts I am getting tomorrow? I ordered a "kit" from Saltwaterfish.com, they should be on my doorstep tomorrow.

As others have said, water changes until the cycle is over is about all you can do.