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I've been fighting a battle with high nitrite levels for weeks now.

Temp 70 deg F

PH - Steady at 7.6

Am - 0 

Nitrite - 2

Nitrate - Had been around 20 but is at 0 now 

GH - 180

KH - 120

I haven't fed the fish for nearly 2 weeks now and the nitrite level isn't dropping at all.

I have a 200 gal FT and 2 grow beds (one is 46"L x 36"W x 11" D, the other is 48"L x 24"W x 5"D) The largest one is full of plants and the smaller is half full of seedlings.

I have already added salt to the tank to help the fish deal with the high nitrite but I'm worried about starving them to death now.

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If you can spare the water and would prioritize the survival of the fishes over cycling, you can do a 30% water change to reduce the nitrite levels. Then you can feed your fishes. (this is just a holding action until your BBs catch up or whatever the  source of high nitrite is addressed).

How many fish are in their and how big are they?

You may also want to dig around the grow beds and look for anaerobic zones which could be causing the nitrate issues. You know you found one when it stinks real bad, like a black garbage can that's been in the 100degree sun all day with the lid on.  That's the smell of anaerobic bacteria in action!

Thanks Chris,

I have 18 fingerlings ranging from 1" to 2.5".

I made the grow beds with a slight slope toward the bell siphons to avoid having low spots where anaerobic bacteria could develop. I've been digging around quite a bit and haven't found any odors, but I'll dig deeper and see what I find. 

If it doesn't improve in the next few days I may have to take Joel's advise and do a 30% water change.


Chris said:

How many fish are in their and how big are they?

You may also want to dig around the grow beds and look for anaerobic zones which could be causing the nitrate issues. You know you found one when it stinks real bad, like a black garbage can that's been in the 100degree sun all day with the lid on.  That's the smell of anaerobic bacteria in action!

Are you in the middle of cycling? Even if it was, with no new feed going in it should be able to catch up with 2ppm being 2 weeks. Not sure what else it could be. If you are cycling, a water change is just going to slow the process down. If you are cycled, a water change is likely a good idea for the fish but until you know the cause, you may end right back in the same place pretty quickly.

Yes, I started a fish less cycle around the beginning of June, but about 2 weeks into it, I stumbled upon some fingerlings for next to nothing and changed my plans. Bad move I guess, but can't change it now.

Anyway, the ammonia, nitrite and nitrate levels climbed, then the ammonia dropped to between 0-0.25 and nitrate peaked out around 40 and has stayed between 0-10 for the last week, but the nitrite hit 2 and has stayed there. I'm wondering if the water hardness may have something to do with it.  I thought maybe the test kit might be bad so I tested tap water and it shows 0.

Chris said:

Are you in the middle of cycling? Even if it was, with no new feed going in it should be able to catch up with 2ppm being 2 weeks. Not sure what else it could be. If you are cycling, a water change is just going to slow the process down. If you are cycled, a water change is likely a good idea for the fish but until you know the cause, you may end right back in the same place pretty quickly.

Maybe both the fish AND the bacteria are hungry :)  Hopefully someone more experienced will see this and reply but if they were at 40 and have cycled down, maybe things are leveling off and that's good. The missing nitrates went to the plants so that's normal.

It's over my head now.

the fish will be fine for a few days with no food..

personally, the second stage of the nitrification cycle lasted longer than the first.. be patient

the ph is ok at 7.6 - add an aerator if you don't already have one...(this helps the whole system, not just the fish..)

They have been 2 weeks with no food already Keith :) 

Feeding them a little should be ok and continue to monitor levels. If your cycled, it should have no problems taking on the food and if anything keep going down.

Keith Rowan said:

the fish will be fine for a few days with no food..

personally, the second stage of the nitrification cycle lasted longer than the first.. be patient

the ph is ok at 7.6 - add an aerator if you don't already have one...(this helps the whole system, not just the fish..)

Being that you are only part way through your cycle your best and safest bet is do water changes and monitor ammonia and nitrite until the bacteria kick in they drop to zero. I would think you could feed lightly if you are changing out water.

I know of a guy who went more than 3 weeks without feeding his fish. Your fingerlings will likely be fine.

Get hold of some water from an established aquaponic system.  The more the better.

When I build systems for people I will kick start the new system with a few buckets of my system water and a small fish load. Using this method in DWC I usually get over the nitrite spike and have nitrates in 7-10 days. With media systems it takes about 14 days. Once I have nitrates I will go to full fish stocking.

I think some media would help more than the water.  I got aquarium water from my neighbor and all it did was mess with my tracking because the nitrates spiked from his rich water.  Still took me 8 weeks to cycle.  Maybe the water changes did slow it down, but I was scared for my fish.

Good news! The nitrite level dropped to 0 :-)

My fish are very happy and eating like pigs (kinda) They ate I gave them, fast.

PH is steady at 7.6, Am is 0, Nitrite is 0, Nitrate is 30.

I took a gallon of water from my sons guppy tank and added it to my FT 3 days ago. The nitrate level in the guppy tank was off the scale by the way.

Anyway, thank you all for the advise and help.

Take care

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