Nirtite High... Everything Else Is Fine?

[MommaJessie]

Okay so I'm new to the fish keeping hobby. I have a 29 gallon, a 10 gallon & 5 gallon... go big or go home right? I've had the same problem with all of my tanks. Very high Nitrite and nothing I do seems to fix the problem.
PH - 7.5
Amm - 0.25
Nitrite - 5.0ppm
Nitrate - 20ppm
Heaters in both & I use quick start, stress coat and aquarium salt during water changes.
No matter what I do my nitrite stays high. I did have 4 adult female guppies in the 29 gallon all of which caught a mysterious illness that wiped them all out. I took down that tank in order to disinfect it. the 10 gallon & 5 gallon have a collective of 30 guppy fry between them. I ruled out over stocking because I had the problem in my 29 gallon when it only had 4 fish. So I guess I'm just looking for tips on what to do. Just started using aquarium salt. I test my water daily & change my water (25%) every other day. Is there anything I can do to fix this problem? Any tips on how to keep my guppy fry alive. They seem fine, no changes in behavior but I'm still worried. I've spent close to 500.00 in the past couple of months and I really don't want my money to go down the drain.

 

[Ninjouzata]

How long have these tanks been set up? What is the stocking of each? What test kit are you using? Are you following the directions for it properly and is it in date?
Have you tried taking a water sample to an LFS you know uses liquid kits to see if the readings you're getting are accurate?
 
Have you tested your tap water?

 

[evan47]

it looks like you are about half way through cycling your tanks. 
your ammonia is being converted to nitrite but your nitrite is not yet being converted to nitrate in sufficient quantity. 
what are your nitrate readings straight from the tap?
it is not uncommon for nitrite to spike for a week or two before settling down and then your nitrate levels will rise.
when i was in this situation (my cycle seemed to stall) i thinned out my stocking by removing the fish with the largest bioload, added some live plants and carried out 30% water changes daily, twice daily when i had the time. 

 

[BenConnah]

Fish excretion process increase nitrite and ammonia levels. So it is good to have less fish in starting of loading up the fish tank.