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New Member
Group: Forum Members
Last Login: 3/22/2013 7:54:21 AM
Posts: 66,
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I have a 100 gallon tank full of feeder fish (medium and large comet goldfish and minnows). The tank is filtered by a Marineland sump with a prefilter and a carbon pad. The tank has great influxes of fish because its a feeder tank and I get the fish in bulk. The system was running fine, everything was cycling properly, ammonia was at 0 and nitrate was less than 10 (I do a 30% water change every week).
But a few months ago, the water became hazy, not quite cloudy. I did a water change, scrubbed the glass and everything seemed fine. The next week I tested the water quality and the pH was at 7.4. I did a 50% water change with the water coming out of the filtered tap water at a pH of 8.0. Three days later I tested the water quality again in the tank and it came up at 7.4. I did another 50% water change with the same results. (I was adding and decreasing the number of fish in the tank continuously through this process and never noticed it affecting or correlating with the water quality.)
Someone that I thought was knowledgable on the subject said some of the dead minnows were finding their way down to the prefilter and that was causing the decrease in pH. I have never heard of this and I can't figure out the science behind his reasoning but I did find dead minnows on top of the filter the last two times I changed it. (I change the prefilter weekly.)
Does anyone agree with what this guy says (we'll call him John) or do you have a different explanation for the reduction in the pH? I would like to get my tank stable again.
Thanks in advance for any help. 
P.S. I am using test strips to measure pH. They aren't expired and I recently bought a new container of a different brand to double check my results.
- 60 gallon - 1 Buenos Aires, 9 Red Serpae, 6 Pristella & 2 Black Neon Tetras, 9 Longfin Blue Danios, 2 Julii Leopard Corys, 1 Rainbow Shark (6 inches, 8 years old), 1 Pictus Catfish (4.75 inches, 1 year old)
- 30 gallon - 2 Comet Goldfish (5.5 inches each, 10 years old), 1 Blue Lobster (3.5 inches, 1 year old)
- 20 gallon - 5 male MM Platies
- 5 gallon - 1 male Halfmoon Doubletail Betta
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Junior Member
Group: Forum Members
Last Login: 10/20/2012 9:58:59 AM
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I'm no scientist, but to me it does not seem possible the decaying matter would alter PH in a tank that size by even .1. If anything I would think it would increase your Ammonia. Did you try testing the water your adding to see if your source has changed? I've heard many stories of water companies making changes to their water which can have significant impact to the PH level. I know in some parts of the country, PH can fluctuate when there is significant rain in the day's proceeding the water change.
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Swifty
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Fish Moderator
Group: Moderators
Last Login: 6/16/2013 6:27:19 AM
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Two possibilities that I know of, although I'm sure there are more.
1 - The nitrogen cycle does have a natural tendency to decrease pH over time. Routine water changes help that so that most of us don't even see it. It's also dependent on the kH of your water. A high kH means that your water will greatly resist the pH lowering and a low one means you might see fluctuations in a very short time
2 - Some city water will naturally go through a fluctuation straight out of the tap. I used to live in a city whose water pH changed from 7.6 in the winter to 7.2 in the summer and back and forth. Even if it's water that doesn't normally change like that, heavy winter snows, heavy rainfall, and many other circumstances can cause a swing in pH, sometimes rather dramatically.
55 gallon
Baby - lionhead/ryukin cross
Westie - lionhead/ryukin cross
Speedy Rodriguez - oranda
Currently searching for a good new tankmate!
planted 29 gallon
3 red eye tetras
4 cherry barbs
2 cardinal tetras
4 albino cories
2 Bolivian rams
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New Member
Group: Forum Members
Last Login: 3/22/2013 7:54:21 AM
Posts: 66,
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I test the pH of my water source before every water change. I'm lucky to have a very stable water source because it comes out at 7.8 to 8.0 every time. I have other tanks too and I do a water change on all my tanks on the same day. The other tanks all have a pH of 8.0. So there is something that I don't understand happening in my feeder tank that is dropping the pH.
- 60 gallon - 1 Buenos Aires, 9 Red Serpae, 6 Pristella & 2 Black Neon Tetras, 9 Longfin Blue Danios, 2 Julii Leopard Corys, 1 Rainbow Shark (6 inches, 8 years old), 1 Pictus Catfish (4.75 inches, 1 year old)
- 30 gallon - 2 Comet Goldfish (5.5 inches each, 10 years old), 1 Blue Lobster (3.5 inches, 1 year old)
- 20 gallon - 5 male MM Platies
- 5 gallon - 1 male Halfmoon Doubletail Betta
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