Sudden Ph Drops In Dp Tank...

[squeakytoy]

Hey everyone... Well, it turns out that Buttercup just had a case of LFS blues... no parasites seen. Yeah! She has put on a little weight, looking a little rounder these days, but I came down three days ago and found her head first in the gravel, looking for all the world like a plane crash! I Reached my hand in to free her, and as soon as I touched the rock, she shot away and hid under the filter intake. Now, being the experienced aquarist I am, I said to myself "hmmm, this might mean something is wrong!" I checked the water, and the ammonia and the nitrites were both zero, but the nitrates were very high, andthe ph had dropped to like 6.4! I pulled a water change with a light gravel vac, and things seemed to go back to normal. I checkd them again just now, and my ph is back down to about 6.2 ! So now I am concerned.

water stats are as follows...
5.5 gal
penguin 200 with carbon and biowheel
ehiem 2224 with ceramic rings coarse floss, bio stone and bio ceramic rings

0 ammonia
0 nitrite
20 nitrate
+/_75 hardness (GH)
0 chlorine
40 alkalinity (KH)
6.2 PH


the tank has java moss and spangle (mini lily pad /clover looking stuff) as well as 2 ghost shrimp. One boat ornament and river gravel for the substrate. Any help would be more than welcome, as I am kinda stumped and not exactly clear when it comes to the hard science of water quality and how they are related.

 

[Colin_T]

If the water is soft, (has little mineral content in it) then the PH can drop rapidly because there is nothing in the water to buffer it. If the GH (general hardness) is about 75ppm then the water is soft and potential has little to no carbonate hardness (KH) in it. KH is caused by any sort of carbonate or bicarbonate in the water. Sodium bicarbonate, commonly known as baking soda is the stuff known to most people. Sea shells and limestone rock are made of calcium carbonate and will help to buffer the KH and PH. You can also buy KH buffers and rift lake cichlid water conditioner. These will all help to raise the KH, and they usually raise the PH too.

GH is the total amount of dissolved minerals in the water and is different from KH. KH being only the carbonates and bicarbonates, whereas GH includes those as well as chlorides, phosphates, sulphates and everything else dissolved in the water.

In a small tank you can put a few bits of limestone or a small bag of shell into the filter or near the outlet of the filter. This will help buffer the PH and stop it dropping as quickly. You will need to add some and wait for a week, monitoring the levels over that time. If the PH continues to drop rapidly then you add some more. Continue adding small amounts until the PH stabilises.

Nitrates will drop the PH so regular water changes and gravel cleans will help keep them low and reduce its affect on the PH.

 

[squeakytoy]

Would I be better served by breaking the shells into smaller chunks, increasing surface area? Also, what might the definition of small be in the case of a 5 1/2 gallon tank? And thanks for the answer... I was doing some looking in the scientific side, and it was pretty in depth. Felt a little like the 37th chamber of Shaolin! Was just waiting for someone to stick their palm through my monitor and say "GO"...

 

[Colin_T]

If the shells are small (less than 10mm diameter) you don't have to break them up but big bits of limestone or coral rubble can be broken into smaller pieces (10mm diameter size) to provide a bigger surface area. You don’t have to break up the limestone or shells and many people have a piece of limestone or shell as a decoration in the tank.
Any shell or limestone should be washed regularly to prevent algae and gunk from covering it and preventing the rock/ shell from buffering the water. I usually just take the bag of shell out and hose it down. Then put it back in the tank.
Try half a cup of shell in the filter and see how it goes. That should be sufficient but you will have to monitor the water over a few weeks and either add more or remove some.