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Nitrites spiking 3 weeks into setup -- please tell me it's OK

Hello all, I'm new to the forum and AP. This is a bit of a misplaced introduction with a critical question.

I've been lurking and learning (thanks for the wisdom), and I set up my system about three weeks ago (pics attached). I have a 55 gallon tank with two grow beds. I have plans to add a third grow bed for this tank and a side tray to grow duckweed in the next few days. There are about 50 fingerling hybrid tilapia in the tank. I like the idea of keeping the fish in my garage because the temp is more constant. When the fish get a bit bigger I have an idea for a 2nd tank that involves pumping water from the tank to a "stack" of long narrow beds on the south side my house.

I've had several tanks in my life, and I'm not afraid to cycle with the fish in the tank. I can see why one would want to cycle first but I'm comfortable with monitoring the setup and making it as easy as I can on the fish.

At this point, I'm just playing around with AP to see if I can make it work. I believe that my job is to set things up and stay out of the way. Nature worked before I got involved, and it will be after ... I'm just trying to harness nature for my own ends.

I started spinach, cilantro, basil, and cukes from seed. The cukes sprouted first and so I put them in even though I have low expectations as to yield with the cukes. I reasoned that the cukes could eat up some of the nitrates while I cycle and while my leafy crops get big enough to plant. The pics are a time lapse from two weeks ago, one week ago, and tonight. The cukes are growing at a crazy rate, which much impressed my wife, who thought it was me that was crazy when I set up the tank and grow beds. 

Anyway, on to my question. My testing (I was away for 6 days) came out pH 7.4-7.6, NH4 0.25, NO2- 5+ppm, NO3- 10ppm. Temp is 74F. My nitrite is off the charts, but it seems to me that this is standard cycling. The fish look healthy but I changed out 5 gal of water and added in 10 gal (there had been evaporation). Do you see anything of major concern here 3 weeks into setup? Do you see anything else with the setup that might cause you concern?

Any help appreciated.

Here's a week ago, and tonight:

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Hi Hank,

So soon after the nitrite spike(couple hours,couple days) you'll be cycled, as you've already suspected. At 74F you'll get there pretty quick. So have some patience. BTW neat setup!

Hi Hank! 

You said  50 fingerling hybrid tilapia in a 50 gallon tank?  That concerns me!  I think you have over stocked. 

Wonderful idea that your ready with the water changes!  How fast will those hybrids grow?

Nitrite was bad news for me but you've got fish that can probably take it.  I'd go easy on feeding or possibly stop feeding until the nitrite goes down but you may know more about it than I do.

Bad for me to George!  Nitrites are just as toxic to fish as ammonia.

George said:

Nitrite was bad news for me but you've got fish that can probably take it.  I'd go easy on feeding or possibly stop feeding until the nitrite goes down but you may know more about it than I do.

Thanks for the replies.

The fish look OK except that the biggest one is respirating really quickly. The smaller ones look good. I'll probably keep changing 5-8 gallons out twice a day until the nitrites come down. If that sounds like too much let me know.

I've never grown these hybrids before, but I know that they grow quickly.

I know that I'll be overstocked at full size, but I think I'll be OK for a couple of months by weight. I have a plan for a second tank and system but I wanted to work through this first one before I built the second.

Hi Hank,

Stocking density is only limited by preference. As long as a system is monitored regularly you can harvest fish or adjust the feeding accordingly. Also, 5-8 gallons twice per day seems spot on!

hey-- this looks familiar. I also started up with two growbeds, one with gravel and one with red lava rock! I'm on day 16 and have the nitrite spike (just under 5 ppm) going as well. I'm outdoors and fishless, though. I'll be adding fish once nitrites drop and the bacteria can clear ammonia I'm adding without any further spikes.

I worried about fish health over the weekend but like Harold said it cycled in a couple of days. I changed water twice a day until the nitrites came down. Now I'm at NH4 0.25, NO2- 0.5, NO3- 5ppm.You expect and you know it's coming but you still worry.

Now I need more plants.

I tried several different things with the GBs. The first two I used piping from Home Depot but the 3rd one (pics coming) I used a screw-together standpipe and tubing from a hydro store and sealed the plumbing with silicone. Also, the gravel proved way too heavy and made me nervous on my old work bench so I got some perlite and layered it so that there is gravel on the floor of the GB and at the top but like a 3-4 inch layer of perlite in between. It seems to work pretty well and it's a lot lighter.

I see that a lot of people here cycle fishless but I had the opportunity to get the fish and was otherwise set up, so I gave it a go and it worked out.

My growbeds are basically plywood coffins with pond liner. I used regular PVC for the plumbing, and my fishtank and sump are IBC totes (the sump is cut to fit below the growbeds, which are propped up on cinderblocks). I'll get pics up here eventually. A little different than yours to be sure, but when I saw the gravel and lava rock, it looked kinda like my setup. I went fishless mostly because I wanted control over how much ammonia was going into the system--it's not like I can ask my fish to crank up ammonia to 2-4 ppm and hold it there. That and I'm planning to stock with catfish and they don't tolerate nitrite nearly as well as tilapia.

perlite underneath the gravel? is any of it floating up (or is any of your gravel sinking down)? I switched to lava rock because the gravel for the first bed was too damned heavy.

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