Tropical Fish Keeping - Aquarium fish care and resources

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bones14 06-29-2010 10:23 PM

ph question
 
I take care of my dad's tanks and when I check his ph its always around 6.0-6.2.The ph from his tap is 7.6.What causes this big of a difference?He doesn't have plants or driftwood.All decorations are the fake aquarium decorations.It always reads about the same so it's stable and I'm not too concerned about it,just curious.

tanks4thememories 06-30-2010 02:30 PM

Quote:

Originally Posted by bones14 (Post 414788)
I take care of my dad's tanks and when I check his ph its always around 6.0-6.2.The ph from his tap is 7.6.What causes this big of a difference?He doesn't have plants or driftwood.All decorations are the fake aquarium decorations.It always reads about the same so it's stable and I'm not too concerned about it,just curious.


Well it appears that he his water has low buffering properties. Apparently he doesn't change much water when he does WC so it is not a major factor. However if you ever have to do a large WC say 50% or more it could be disastrous. Here is a link on pH that may explain a few things for youhttp://tanks4thememories.blogspot.co...n-ph.html#top1
GL!!:-)

bones14 06-30-2010 05:45 PM

I do his water changes for him and change about 30-40%.I can't do his on a regular schedule because of work,3 yr old,etc...so its usually about every 3 weeks.

bones14 06-30-2010 06:07 PM

Another thing is we're on the same city water and mine doesn't drop that much.My ph is 6.8-7.0 with live plants and driftwood.

Byron 07-01-2010 12:04 PM

You need to be careful. First, infrequent water changes on tanks without plants is why the pH is dropping so much. Several things can affect this, such as the type of fish and their number, plants, wood, frequency of partial water changes, feeding schedule. As the previously-linked page explained, aquarium water will naturally become more acidic over time, unless there is something to prevent this, such as calcareous minerals whether in the tap water (the carbonate hardness factor that buffers the pH to a certain point) or in the tank (limestone, dolomite, coral gravel, rock, etc). A regular significant partial water change also works to keep the tank water chemistry more stable. This is all well and good, but along with the drop in pH some other things occur.

Nitrosomonas bacteria cease to multiply the lower the pH (6.5 is sometimes given as the number) and many authors say at 6.0 the bacteria will not multiply at all and actually die off. This is not all that critical if the water stays acidic, because in acidic water ammonia (produced by the fish and biological actions in the tank) automatically converts to ammonium which is basically harmless. So with a gradual decline in pH, the fish manage (unless of course they are hard water fish, in which case this is slowly going to weaken them and cause other health issues). Then the trouble comes with the next "large" water change with tap water having a basic (above 7.0) pH.

The sudden influx of basic water causes the pH of the tank to rise, and if it rises above pH 7 the ammonium immediately changes back into ammonia, and the bacteria which have been reduced (or perhaps decimated) by the acidic water cannot multiply fast enough (it takes 9 hours for nitrosomonas bacteria to multiply and 20 hours for nitrospira, at optimum conditions) and the fish get ammonia poisoning and may be severely weakened or killed.

In planted tanks (and by planted I mean well-planted) there is less risk because plants use ammonium and have the ability to change ammonia into ammonium faster than nitrosomonas bacteria. This is why in a well-planted tank with a moderate fish load one can actually get along fine with no water changes ever, or maybe one or two a year. The plants do the work, provided the fish are not out of balance. But in non-planted tanks allowing the water to alter its chemistry through infrequent water changes is bound to cause trouble one day. A weekly partial water change of 50% is in my view essential in non-planted tanks, unless the fish load is very light and the tank large.

tanks4thememories 07-01-2010 06:09 PM

Quote:

Originally Posted by byron (Post 415651)
you need to be careful. First, infrequent water changes on tanks without plants is why the ph is dropping so much. Several things can affect this, such as the type of fish and their number, plants, wood, frequency of partial water changes, feeding schedule. As the previously-linked page explained, aquarium water will naturally become more acidic over time, unless there is something to prevent this, such as calcareous minerals whether in the tap water (the carbonate hardness factor that buffers the ph to a certain point) or in the tank (limestone, dolomite, coral gravel, rock, etc). A regular significant partial water change also works to keep the tank water chemistry more stable. This is all well and good, but along with the drop in ph some other things occur.

Nitrosomonas bacteria cease to multiply the lower the ph (6.5 is sometimes given as the number) and many authors say at 6.0 the bacteria will not multiply at all and actually die off. This is not all that critical if the water stays acidic, because in acidic water ammonia (produced by the fish and biological actions in the tank) automatically converts to ammonium which is basically harmless. So with a gradual decline in ph, the fish manage (unless of course they are hard water fish, in which case this is slowly going to weaken them and cause other health issues). Then the trouble comes with the next "large" water change with tap water having a basic (above 7.0) ph.

The sudden influx of basic water causes the ph of the tank to rise, and if it rises above ph 7 the ammonium immediately changes back into ammonia, and the bacteria which have been reduced (or perhaps decimated) by the acidic water cannot multiply fast enough (it takes 9 hours for nitrosomonas bacteria to multiply and 20 hours for nitrospira, at optimum conditions) and the fish get ammonia poisoning and may be severely weakened or killed.

In planted tanks (and by planted i mean well-planted) there is less risk because plants use ammonium and have the ability to change ammonia into ammonium faster than nitrosomonas bacteria. This is why in a well-planted tank with a moderate fish load one can actually get along fine with no water changes ever, or maybe one or two a year. The plants do the work, provided the fish are not out of balance. But in non-planted tanks allowing the water to alter its chemistry through infrequent water changes is bound to cause trouble one day. A weekly partial water change of 50% is in my view essential in non-planted tanks, unless the fish load is very light and the tank large.

Excellent post!!!! Your understanding of the principles involved is only exceeded by your awesome ability to explain it.

bones14 07-01-2010 07:04 PM

I'm just gonna have to try to get the water changes weekly then.Once again excellently explained Byron.So I'll start with smaller water changes and work my way to 50% weekly.His tank is 30g and way over stocked.I keep trying to tell him but he's stubborn and doesn't listen.

tanks4thememories 07-01-2010 07:41 PM

Quote:

Originally Posted by bones14 (Post 415832)
I'm just gonna have to try to get the water changes weekly then.Once again excellently explained Byron.So I'll start with smaller water changes and work my way to 50% weekly.His tank is 30g and way over stocked.I keep trying to tell him but he's stubborn and doesn't listen.

Well once you hit 50% weekly then I would slowly work my way down to bi-weekly depending on what pH readings you get.

Byron 07-01-2010 07:59 PM

Thank you sincerely for the credit, but notwithstanding your kindness I am going to have to disagree with you on this last post.

A tank without plants (which I am assuming this is, I apologize if I err in this assumption) should have a weekly partial water change especially if it is, as stated, "overstocked." There is simply no other way to create a healthy environment for the fish in that tank.

I won't go into all the scientific data here, we discussed this not long ago in another thread or two, and as there I will refer you to the excellent articles in the November and December 2009 issues of Tropical Fish Hobbyist on water changes. They are well written and the author conducted many tests to arrive at his data.

Doing water changes based on tests for pH, nitrates, or whatever is not sufficient. For one thing (and only one), fish release pheromones into the water, other fish pick up on these and it causes them stress in various ways. You can't test for these, and no filter removes them; only regular weekly water changes will help. And as the author of those article said, a daily 50% water change would be great, but who among us can handle that? But weekly doing 40-50% (or more depending upon the stocking, he recommends 70% weekly for normally-stocked aquaria) has been shown to be effective in reducing issues for fish.

Byron.


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