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Old tank syndrome

Soilwork

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22 Nov 2015
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456
Has anyone ever had a situation where the tank has failed (fish deaths etc) that they could categorically say was caused by old tank syndrome i.e ph crashing due to kh depletion or build up of minerals etc?
 

tam

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5 May 2011
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Fish didn't die, but my parents had a tank that pH crashed (kept dropping to around 5 if I remember right -measured with a pen) due to kh depletion - high nitrates and no kh. Would return to normal with buffer. It had been a bit neglected and gone from plants to no plants due to a planting eating fish being added. Fixed with more water changes and using higher gh/kh base water to start with.
 

Soilwork

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22 Nov 2015
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Fish didn't die, but my parents had a tank that pH crashed (kept dropping to around 5 if I remember right -measured with a pen) due to kh depletion - high nitrates and no kh. Would return to normal with buffer. It had been a bit neglected and gone from plants to no plants due to a planting eating fish being added. Fixed with more water changes and using higher gh/kh base water to start with.
Fixed assumes that the tank was broken. Were their any issues with the fish etc?
 

dw1305

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Hi all,
When started keeping fish (in the 1970's), I didn't change any water and every 6 months of so, <"most of the fish would die">. I didn't use a filter, and although I had plants, the light of a tungsten filament bulb was definitely inadequate for plant growth. Looking back on it it was amazing they lasted as long as they did.

Needless to say I didn't test the pH, but because I was already using rainwater, so <"old tank syndrome"> must have been a possibility for the fish deaths. I also recall deaths after a water change, which may have been pH related, in this case because the pH rose and NH4+ was converted to NH3.
It had been a bit neglected and gone from plants to no plants
My guess is that you can't really get "old tank syndrome" in a planted tank, all the time you have active plant growth, even if you don't change any water, but just top up evapoaration.

cheers Darrel
 

Affinis

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6 Sep 2019
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My guess is that you can't really get "old tank syndrome" in a planted tank, all the time you have active plant growth, even if you don't change any water, but just top up evapoaration
I’ve seen some really extreme examples of water chemistry from customers tanks over the years. Typically you’d see zero Kh, 30+ GH, very low pH, sky high nitrate and TDS levels 900 plus.

Some of my tanks haven’t been water changed for over a decade, but being jungles they’re much more stable, but I do have to top up mostly with rain water to prevent the TDS rising.
 
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tiger15

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14 Mar 2018
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I used to keep African cichlid tanks and did not change water for months. My tank water started out with mildly hard tap water of pH 7.6, kH 4, and TDS 100 and gradually degraded to pH<7, kH>10, and TDS>400 over months. In fact, I used parameter change as a timer for my next water change which could be several months apart. My fish were not doing well. While hardy species from Malawi did OK, sensitive species from Tanganyikan often died early from bloat or self imposed starvation. After I changed my habit to do regular WC weekly, there was no more pre matured death. I don't think my fish were negatively impacted by the parameters I measured, but more likely impacted by accumulation of unknown toxic chemicals such as heavy metals and organic compounds that I did not measure.

Not doing regular water change is a time bomb for fish only tank known as old tank symptom. With plants, the dynamic is different as plants are known to uptake heavy metals and organic compounds and as such, have been utilized by wastewater treatment plants to cleanse nutrients.
 

tam

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5 May 2011
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Fixed assumes that the tank was broken. Were their any issues with the fish etc?
Yes, cloudy eyes - which can be associated with poor water quality.

I think plant growth is very helpful for stabilising things, logically it gives somewhere for the 'stuff' building up in the water to go, whether that's locked in the plant material, or in plant material that's then removed from the tank. It's another way of taking something away from the tank instead of just adding more.
 

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