Fish Tank Carbonate Alkalinity and PH

Another scenario unfolds in the usual fish tank. There is a collection of Koi, goldfish and pond fish. The water was changed two weeks ago and a satisfactory amount of carbonate alkalinity existed in the system. Daily, the fish are fed, and the filter reduces the nitrogenous wastes. The Hydrogen is bound out by the carbonate alkalinity and all is well, until two weeks later the carbonates are exhausted. The owner of the Koi, goldfish and pond fish collection is lulled into a false sense of security because the pH has been stable for weeks. Why check it?

The carbonates finally “poop out” and truly overnight, the fishes’ carbon dioxide production, the algae’s carbon dioxide production, and the reduction of the Ammonia in the filter crashes the pH to 5.5 and the collection is all but lost.

Using a commercial buffer like SeaChem’s Neutral Regulator (yes it has phosphates but it’s my favorite) or Baking Soda on a regular basis to maintain a Total Alkalinity over 100 PPM would prevent this completely. I advise many of my Georgia (soft water) clients to apply a neutral buffer every week.

So, what should you do if your pH is crashed?

1.      First, net the dead. There’ll be plenty.

2.      Then apply the recommended dose of commercial pH buffer. You could substitute Baking Soda. Use three to five teaspoons of Baking Soda per ten gallons.

3.      One might wonder at this juncture about the decades-old legend that you should never change the pH of a system by more than a quarter point per day. This is archaic. Indeed, the most successful approach which will save the most fish lives is to raise the pH into normal range as quickly as possible. If you were in a smoke filled room, would you want me to remove you from the room quickly or gradually?

 

The clinical presentation of a pH derangement will follow the following steps depending upon "how bad" the pH is.

-          Initially, as the pH begins to decline you will notice that when at rest, the fish tend to remain near the surface. Energy levels decline.

-          As the pH drops a little lower, appetite suffers.

-          Shortly, as the pH drops another point and nears 6.0 you'll see a milky skin.

-          As the pH drops even lower, the fish loses slime in strands as the skin burns. The fish will be very depressed and either descend to the bottom to die or they may gasp at the surface.

-          Death follows this scenario.

 

Remedies for pH problems include commercially available buffers. I use these most often. You can also use Baking Soda but there are two defects: First, Baking Soda does not reside in the system for very long and it has no 'staying power' or residual value.

Secondly, Baking Soda does not buffer to "neutral". Indeed, the pH follows a radaical upward swing to pH 8.3 and then seems to gravitate downward to about pH 7.6 at equilibrium. I have no doubt that there is an explanation for this, but I don't know it. The clinical relevance is that a customer who uses Baking Soda in carbonate depleted waters is doing the right thing, and can be reassured that the high pH achieved will coast back down into the "sevens" within six to eight hours.