Mysterious Deaths in my Aquarium.

In my Walstad setup, whenever there is a large 50% water change, my snails use to die in next 24-48 hrs. These death use to be mystery for me, but finally I found the problem. It’s the ‘Old Tank Syndrome’.

Old Tank  Syndrome is a series of events. First, the nitrate cycle converts ammonia into nitrate. This is good, but in doing that it releases acid. This 

consumes carbonate buffer, just like mixing vinegar and baking soda. Slowly, but surely, this leaves your tank ever more acid in pH.

At some point, the water becomes acid enough to start shutting down the bacteria. This starts at around pH 6.5 and "all" conversion stops below pH 6. Ammonia starts to form, but it's "ok" because acid water converts the deadly Ammonia form to the far less deadly Ammonium form.

This state of Lower Ph (acidic water) and high Ammonium is called the ‘Old Tank Syndrome’. Most of the fishes by now have got adjusted to this acidic environment.

All seems fine, until you change the water in a tank with Old Tank Syndrome (OTS). Adding new fresh water cause the pH to bumps up. This instantly 

converts all of the Ammonium back to Ammonia, and your fish suffocate and die due to ammonia burst.

Plants consume ammonia directly, But if your pH is 6, or below, you must be careful – no matter how old your tank is. Plants, continue to work as long 

as they are in their pH ranges.

Warning signs for OTS: Persistent pH 6, or below is a classic sign of OTS. 

Remedy:

-        Gradually Raise the Water Ph by increasing the Buffering (KH).

-        Make smaller 10-15% water change every 3 days instead of large 50% water change.

To take care of this acidic water, one can add some carbonate or bi-carbonates into the aquarium.

Eg:  Sodium bi-corbonate (Baking soda) for instant relief.

Crushed coral, sea shells in all its forms, is Calcium Carbonate. It dissolves slowly, and is a fine source of both KH and GH.

By slowly  adding bicarbonates, the acid will be neutralized and the ph will be raised gradually. Any more acid created by the bacteria will be absorbed (neutralized) by dissolved bicarbonates in water.

Also remember if you have snails, then these folks are also gradually depleting the water of carbonates/bicarbonates to make their shell.

Buffering helps you to maintain your PH levels.