Old fish?

[Seashellz]

I own 5 zebra danios that are all 100% healthy except my really big one, he used to be aggressive and lively always begging for food and now he sits in the corner of my tank or hides in the log, no growths, fin problems or anything. and none of my other fish are acting strange

Water parameters.

Nitrate: 0

Nitrite:0- very low

Ph: 6.5

KH:120-180

Gh: 60- 120

 

[Seashellz]

Forgot to mention I have only had the fish for 2-3 years

 

[jwh0818]

What's your ammonia level? What's your water change schedule? How long has this tank been running? Do you replace your filter pads? You shouldn't. Also what size tank is it?

 

[Seashellz]

Ahhhh here we go yes I changed the water yesterday like I do every week and changed the filterpad recently and ammonia is 0

- the fish was acting strange before the water of filter pad change

 

[jwh0818]

Ahhhh here we go yes I changed the water yesterday like I do every week and changed the filterpad recently and ammonia is 0

- the fish was acting strange before the water of filter pad change

Okay well never change your filter pads unless they are falling apart. When doing a water change put tank water in a bucket and swish the pas around in the old water. This save your bacteria that keeps your tank running smoothly. You shouldn't be seeing nitrites without ammonia do I would advice a 50% waterchage now and add prime with the new water. Wait an hour after that and retest all parameters. Your likely seeing the fish are being poisoned by the nitrites if there are any.

Do you know how to properly cycle a tank?
What size tank?

These are great to read.

http://www.aquariumadvice.com/i-just-learned-about-cycling-but-i-already-have-fish-what-now/

http://www.aquariumadvice.com/important-information-for-those-new-to-the-aquarium-hobby/

 

[Seashellz]

Yes I know how to cycle a tank

 

[jwh0818]

Yes I know how to cycle a tank

Okay what size tank and what other fish are in it?

 

[Seashellz]

10 gallons an 4 more Zebra danios

 

[bribo12]

I'm pretty sure they only live 3-4 years. So you've probably had it most of it's life

 

[Seashellz]

Ahhh then that is probably the answer then because I have no other problems with any o my other fish