Biological media problem

[Stanster59]

Hi , have a Juwel lido 120 and recently decided to some more biological media after seeing a filterpro you tube video.
Bought some biogravel with the intention of adding a further 1000g of the media into the bottom filter housing ( in fact only got 2 x 300g portions in , added over two.weeks) but since then my fish have been dying, tetras and city's so far).
Water parameters seem fine , pH 7-8, Nitrate 20 ppm, KH 8, GH 13.

Any suggestions ?
Ta.

 

[Naughts]

Can you test ammonia and nitrite? They occur in uncycled tanks and kill fish.

 

[Colin_T]

The best filter media is sponge. It lasts for years, traps gunk and holds beneficial filter bacteria.

 

[Slaphppy7]

The best filter media is sponge. It lasts for years, traps gunk and holds beneficial filter bacteria.

I disagree, sponges are nasty...gimme ceramic media instead.

 

[Stanster59]

Can you test ammonia and nitrite? They occur in uncycled tanks and kill fish.

Data in my post, all ok.

 

[Stanster59]

I disagree, sponges are nasty...gimme ceramic media instead.

I was adding additional material,kept existing sponges and ceramic media.

 

[Slaphppy7]

Data in my post, all ok.

You don't list your nitrIte levels and ammonia levels.

 

[Naughts]

Data in my post, all ok.

Ammonia is excreted by fish and, in an uncycled tank, will build up and poison them. When cycling, ammonia is converted to nitrite which then builds up and poisons the fish. You don't have readings for ammonia and nitrite. What are they? We need to know the ammonia and nitrite levels to help identify what is killing the fish.
The presence of nitrate (the end result of beneficial bacteria breaking down ammonia and nitrite) may just reflect the tap water rather than a cycled tank.
How did you cycle the tank?

 

[Naughts]

BTW, adding filter media (assuming it is a reputable source and intended for aquarium use) is highly unlikely to be a cause of fish deaths.

 

[Stanster59]

You don't list your nitrIte levels and ammonia levels.

Yeah, sorry, they were normal

 

[Stanster59]

Ammonia is excreted by fish and, in an uncycled tank, will build up and poison them. When cycling, ammonia is converted to nitrite which then builds up and poisons the fish. You don't have readings for ammonia and nitrite. What are they? We need to know the ammonia and nitrite levels to help identify what is killing the fish.
The presence of nitrate (the end result of beneficial bacteria breaking down ammonia and nitrite) may just reflect the tap water rather than a cycled tank.
How did you cycle the tank?

It's a mature tank, I was just adding more new media

 

[Naughts]

So have you tested? Or are you just assuming?

 

[Stanster59]

So have you tested? Or are you just assuming?

Tested.

 

[Naughts]

Good, so the numbers are...?

 

[Stanster59]

Ammonia 0.5, Nitrite 0.5, Nitrate 20ppm.

NTL aquarium test kit.

Only fish left are some green neon rasbora , sparkling gourami and 1 peppered cory