Ph Drop

[TheycallmeFishMan]

Hello all, I'm experiencing some unusual problems with one of my tanks. (I have 9) but the one I'm having the problem with is actually 10 years old! I'll upload pics, beautiful tank, crystal clear water, all levels have been fine even PH, up until now. All levels test 0 besides ph and nitrate. Nitrate was at .5, and my PH is a scary 6.0 or less. It was at around 7.4 for the longest time. The tank gets weekly water changes, using stress coat. The only problem I have with this tank, is a black/algea but it's not horrible. I just clean it when it starts to show. (Haven't tried any algea fix or algea rid yet) ... the tank went under a few changes about 2 months ago. I changed out the blue gravel, for some new Blue gravel, (I know you shouldnt, but I had my reasons) and a month prior to that, I changed from a Bio Wheel to a API 70G. Filstar. Never went through any spikes, or a new cycle, just the ph drop. I did recently rinse my filter and cleaned the media (about 3 weeks ago) again, no cycle or spikes occured. I tested the water several times after and all was good. Just recently I've lost several fish I just added, and a gourami that didn't look all that healthy to begin with (had him for 3 months, died today) ... the tank is a hexagon oceanic. It's the only tank I'm not positive of size. Which is why I haven't used the algea meds. But anyways the tank has :
2, 2 1/2 inch barbs.
3, 1 inch or less tetra.
Albino pleco that's around 2 inches.
4 platy less than inch
3 dalmation mollies measuring 1 inch (that are very aggressive)
And a 2 1/2 inch Pearl Gourami

 

[eaglesaquarium]

Well, nothing is jumping out at me as obvious.  How big are your weekly water changes?
 
 
It is possible that the water change amounts could be higher and it could be a bit of an old tank syndrome.   
 
 
I'd suggest changing your water at the same level, but two or three times a week for a while.  Then after 3 weeks, do a 50% change.  Then a 75% the week after.  That should take of it if its OTS.  And if its not... it shouldn't do any harm.

 

[Byron]

I see a couple things, but let's start with the pH.  The pH is relative to the GH (general hardness) and KH (carbonate hardness or Alkalinity).  It is natural in all aquaria for the pH to lower over time; this is due to the accumulation of organics that are broken down by various bacteria which produces CO2 and this creates carbonic acid so the pH will lower.  Organics added to the aquarium (such as wood, dry leaves, peat) will contribute to this as well.  However, the rate this will occur, if at all, depends upon the buffering effect of the GH/KH.  Regular partial water changes also influence the process.  And any calcareous substances in the tank will impact it as well.  The issue JD mentioned is related to all this.
 
With that brief explanation, let's go to specifics.  What is the GH, KH and pH of your source water (presumably tap water, or well water)?  We need the numbers for the water out of the tap.  If you don't know, you should be able to ascertain these from the municipal water authority on their website.  Or you can use a test kit yourself if you have one, but check with the water folks first as we only need to know the numbers once.  If you do test the tap water pH, remember to out-gas the CO2 first or you may get a false reading.  CO2 in the tap water lowers pH just as it does in the aquarium as I explained above.
 
Once we know the numbers of the source water, we will have a better idea of what may be occurring, and how to deal with it, if you need to.  It would also help to know what the pH shows for your other tanks.
 
That's the pH for the moment.  Now to a couple other things.  First, never use algeacides in a tank with fish.  Any and every substance added to the water in an aquarium gets inside the fish, and at the very least will cause stress and possibly internal issues.  There is only one safe way to deal with algae, and that is to balance the light and nutrients to keep it under control (if those are live plants, can't tell from the photo).  I won't bog things down with more on this, but we now come to the Stress Coat.  I wsouldnot use this product; it contains aloe vera, and there is now scientific proof that this has the ability to harm fish.  Won't go into the science, but it is not a substance that belongs in a fish tank.  Any conditioner that detoxifies chlorine/chloramine but does not contain other substances like Aloe Vera will do.  I use the API Tap Water Conditioner, but there are some others.
 
Byron.