Lethargic Fish Help Please

[Asteria]

My killifish wasn't very active yesturday and was holding his fins close to his body

He's now just sat on the bottom pretty much in active, wobbling a little
There is no filter flow.

0 nitrates
0 ammonia
7.9 ph level

50% water change yesrurday and added a little revitalizer tonic

I have pictures too

He eats also. No marks on him or anything

 

[Asteria]

Ooo he's perked up a bit now
But he's still sitting on the bottom

 

[wrightt3]

What killifish is it?     How long have you had it?
I know some only live for about a year or so because in the wild their habitats dry up in the dry season...

 

[Asteria]

Golden lyretail
Maybe just about a year
But I have had a another for longer

 

[wrightt3]

The golden lyretail has a longer life expectancy than most killifish (3 years ish) so its not that then. 
You say your nitrates are zero, they shouldn't be! Ammonia and nitrite should be zero and nitrate should be about 5-20 ppm.
Was this just a spelling error?

 

[Asteria]

Ahaha sorry I'm actually using my phone
Spelling mistake xD
My nitrate is 5ppm

 

[wrightt3]

In that case i have no idea, most diseases only occur due to poor water quality and yours seems fine. If he is eating fine and is looking fine then this may pass in a few days. Do you have anything else in there with him?

 

[Asteria]

Yeah that's why I'm stumped
His girlfriend xD

And then a female guppy.
They are all fine together

 

[the_lock_man]

What are you testing the water with?
 
When you say there is no filter flow, could you expand on that? I'm wondering if it's a lack of oxygen, since it is the filter out-flow that should be rippling the surface of the water, to encourage proper oxygenation of the water. You'd think the fish would be gulping at the surface if that were the case, but....

 

[Asteria]

Sera test kit, not strips

There is a filter running, but there is a devider blocking the flow of the filter output
I actually have two running

 

[wrightt3]

Is the divider completely blocking the flow? It may be preventing proper filtration.

 

[Asteria]

No not complete flow, there is a very gentle amount of it.
But he seems better now
More happy
And why would it just effect him and none other fish ?

 

[wrightt3]

If he seems that he is getting better then it may have just been a grumpy phase he was going through lol
I would just keep a close eye on him for the next few days to look out for anything unusual.