Old Tank Syndrome (sindrome de un acuario viejo)

Que pasa cuando uno tiene un acuario no plantado y ademas no le hace cambios de agua ni nada?

In an non-planted tank it would develop into Old Tank Syndrome.
But the activities of the plants limits this nasty result.

Old tank syndrome happens when a fish-only tank does not get enough water changes/gravel vacs.
The organic matter (fish poop and food in varying stages of decomposition) builds up.
The bacteria that decompose these materials use oxygen (which is replenished by water circulation) and some minerals, including carbonates, which are replenished with water changes (but this is a tank with not enough or no water changes).
The bacteria population crashes. The mulm continues to build up, and ammonia becomes noticeable. With no KH (bacteria used it all), the pH drops, so the ammonia is present as NH4+, not so toxic to the fish.
Over time, before the bacteria crashed, they were very busily making NO3. Levels can reach triple digits!

Now, you are looking at a tank with very low mineral levels, very high NO3 and NH4 levels.
When you do a water change (presumably the tap water has minerals) the fish may die. Too great a change in TDS.
When you add new fish, they die. The old fish acclimated to the toxic level of NO3 over time, but new fish cannot handle it.
The solution is to do very small, frequent water changes, like 10% daily until conditions improve, and you can do larger water changes. Ultimately the mineral level rises and the fish acclimate to that, and the nitrogen is removed in all its forms.


Ahora bien, que pasa cuando es un acuario plantado?

How this is different in a planted tank:
You are adding minerals, and monitoring the levels of KH and everything else. The way out of line nitrogen is much less likely to happen because you are monitoring it. The plants are using the nitrogen as fertilizer, too, so removing it from the water.

I could see a few issues, though:

Some bacteria can grow when there is more mulm in the tank. Including the bacteria that cause fish diseases.
Medications often can get locked up in organic matter, so do not hit their target. If you need to medicate a tank it is much better to do a thorough water change first.
A thick enough layer of mulm builds up and can cover low growing plants, excluding light, so they can die. Some might just grow taller to get above the mulm.
As organic matter is broken down in the tank it releases many nutrients for the plants including all the things we add as fertilizers, and CO2. This is the basis for a slow growing natural tank. The low levels and constant supply of nutrients is balanced with the relatively low light, and the plants are happy.

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Sin embargo, debo destacar que la acumulacion de materia organica osea los compuestos organicos pueden crear 2 cosas. Una de ellas es lo que dice este articulo, las bacterias combierten el mulm y la materia organica en nutrientes para las plantas nuevamente (el natural) o si no hay la suficiente oxigenacion y flujo de agua la bacteria no puede hacer esto muy rapido por lo que esto crea algas. Por eso es necesario tener un buen filtro, sinfonear el fondo de vez en cuando, tener un buen flujo y hacer los cambios de agua parciales cuando tenemos un Med-Tech o un High Tech que es lo que todo el mundo tiene por lo general.

Los cambios de agua me han dado buenos resultados en los acuarios, esto combinado con la limpieza parcial de los filtros.

Yo recomiendo al menos un cambio de agua de un 25% cada dos semanas para un acuario bien estable, mayormente bien plantado. Recomiendo 25% semanales a todos los acuarios en general y un 50% semanales si usan el EI dosing o si tienen problemas de algas.

Recuerden siempre, despues del cambio de agua fertilizar, no importa si hay algas o no.