Neon Tetra died!

[Byron]

Surely a healthy tank has a lot to do with the biology though, and if water changes are needed that often the tank isn’t capabale of dealing with the waste that’s in it? Meaning the tank isn’t healthy to begin with. Water changes don’t happen in the wild and a tank is no different with the right set up, if the substrate is deep enough surely the waste will just been drawn down and broken down?

Some misunderstandings here. First, fish habitas have eben more water changees than we could ever do in an aquarium, unless it was flow-through. But I suspect noone on TFF has this, so water changes are mandatory, and the more the better. In th habitat, the fish do not live in the same water from second to second. That is a major water change. Fresh water is continually flowing downstream.

It is not the waste itself, but what it becomes. Bacteria primarily in the substrate break any organic matter down. This releases ammonia and CO2 which are extremely beneficial if you have plants. The waste gets broken down, but what it contains is still in the system until we do a water change.

 

[sharkweek178]

The filter removes bits floating in the water. The bacteria in the filter remove ammonia excreted by the fish. Nothing removes all the other things excreted and secreted by the fish. We do water changes to remove those things.
Fish, and plants where the tank is planted, remove minerals from the water. Water changes top up these minerals.

Even though the water looks clean, you can't see the things dissolved in it. If you dissolved a spoonful of salt in a glass of water it would look like pure water. It's the same with tank water.

I was just talking to someone about this the other day. It's not the stuff you can see in water that's dangerous. Fish can live fine in green or muddy water. It's the stuff you can't see.

 

[Endlersendlers]

I noticed in an earlier post the OP found a source that overlapped water temps and stated plecos and tetras can live together since they occupy different parts of the water column. Of course they liked that source because it said what they wanted to hear, and then used it to decide all was good. While their intentions are good, we tend to look for optimal conditions at which fish thrive, not just survive for a little while, and can live out their expected life spans, so we look to sources that are expert based, and not just anecdotal experience. The difference is not immediately apparent as most people think everything was fine until the fish don’t act right and die off prematurely one by one, never knowing something was not right for that species and they can’t live out their full lives in the conditions they were in as it is causing permanent damage.

 

[Naughts]

I have been following father fish who advises...

Surely I don’t even need to change the water if it’s healthy or clean the tank that often...

You are reporting a dead neon and the remaining fish so stressed they are swimming into the side of the tank. You also have dangerous if not fatal levels of nitrite and nitrate.

It might be time to change it up.