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Old 10-01-2010, 02:45 PM   #1
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Rescue Aquarist

Anyway, I am newish here, but have lurked, and maybe was active before. I don't recall...

I do have one question: my tap water, which I age and condition, has a pH of about 7.8. My tanks are all in the upper 6 ranges, like 6.6, or 6.8. I put shell bits in to add some minerals to the water. Q: Where is the acid coming from??

I have several small aquariums that exist for the fishy survivors of biology classes attempts at eco-system modeling. Don't scold me, I was against it too. I used the keeping of the aquariums as an example of an ethical way to respond to what I thought was an ill-conceived enterprise.

I have a pleco, guppies, guppies, and goldies.
The goldies get a new tank this weekend--almost 40 gallons. That will be ten gallons per fish, so that should be a treat for them. It will be, as are all of my aquariums, heavily planted and well lit.

All of my tanks are stable, with no ammonia, and some nitrates. The smaller guppy tank--5 gallons & 7 guppies--has no nitrate either, so I add some water from a larger tank to sustain the plants in the smaller.

I use Aquaclear HOB filters with sponge, bio-media, and Purigen, and I have more than adequate filtration throughput, and the tops are mostly open.
I vacuum the bottom once a week and at the same time do about a 25% PWC and clean the filters by rinsing out junk and changing my prefilter.
I feed once a day usually, and only as much as they can eat in about a minute or so.
The Goldies get flakes, Topfin.
The Guppies get a variety of foods, Hikari powdery foods like daphnia or spirulina.
The Pleco gets Hikari veggie-tabs of some sort, and some zucchini once or twice a week.

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Old 10-01-2010, 03:20 PM   #2
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It is natural for PH to drop in a closed environment. How much and how often do you feed your fish? What do you feed your fish? How often do you clean your filters? How often is your 25% PWC? Do your tanks have open tops or are they covered?

Happy Reefing,
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Old 10-02-2010, 02:39 AM   #3
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Welcome to AA. how long do you wait before you test your tap water?
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Old 10-02-2010, 09:51 AM   #4
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Put some tap water into a container, let it sit overnight, and then test the pH. Tap water is often pressurized and thus the equilibrium level of gasses (most significantly CO2) is different fresh out of the tap versus after it has some time to adjust to ambient atmospheric pressure. This could impact the pH. I suspect that once you let the tap water sit overnight, you will find the pH a little lower than 7.8. Might not be in the 6's, but probably in the lower end of the 7's rather than the upper end.

Any driftwood in the tanks? Tannins are acids, and so tanks with lots of driftwood often see a pH creep downwards.

The only other cause I can think of is the natural operation of the ammonia cycle. Remember that fish excrete ammonia, which is NH3. When all is said and done and the biofilter has processed that, it is nitrate, NO3. Which means each molecule of ammonia is eventually spitting out 3 hydrogen ions--acid.

If the cause is this latter process, then you have only a few options. You can reduce the bioload (fewer fish and/or increasing the size of the tanks). You can do PWC's more frequently, or make them larger than you currently do (maybe 50% rather than 25%, though larger PWC's also have the potential to be more stressful on the fish so that is a factor to consider). Or you can increase the buffering capacity of your tanks so that the acid generated by the nitrogen cycle is less able to impact the pH.

The latter option might be the easiest since you say you run a HOB filter. I've never used Purigen in any tank so I'm not quite sure exactly what its purpose is, but my first reaction is to tell you to forget the Purigen and instead replace it with a small mesh bag of crushed coral. The fact that the filter water is flowing through the crushed coral will keep the water well-buffered. If you feel you absolutely need to keep the Purigen in the HOB, then another option would be to take a mesh bag of crushed coral and just hang it in the tank, ideally near where the HOB outflow flows back into the tank so that there is constant water movement around it. Back in the previous city I lived in my tap water was roughly neutral and had very little KH (carbonate hardness, which accounts for buffering) and so my tanks were subject to some pretty wild pH fluctuations. Once I started hanging a bag of crushed coral near my HOB outflow, the problem was eliminated. I just suggested putting it in the filter itself because, well, it's out-of-sight and not a distraction in the tank.

Please keep us posted on what you end up doing and the results.
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Old 10-04-2010, 02:59 PM   #5
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Well that makes sense...

I certainly don't have underpopulated tanks, but I do keep them clean enough that there are not NH3 or NO2 problems, or algapaloozas. No doubt there is quite a bit of nitrification at work, though, so those pesky protons are probably to blame. I could easily do more PWC, and suck more crapola off of the bottom.

I had hoped that the shells that I add, and the Seachem Neutral Regulator product would buffer at neutral, but not only does that not seem to be the case, but it is apparently the wrong product of theirs for the planted tank (which mine are). I do need to add more of the carbonate source to buffer the tanks.

I have not waited long before pH'ing the tap water. I am gonna do that today and see what the deal is.
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Old 10-04-2010, 03:13 PM   #6
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You may want to check on the quality of your Seachem Purigen in your filters. Just like other "Impurity Absorbers" - Purigen can "fill up" and then once it does - it will begin leeching by-products of what it's gathered back into the water.

From Seachem's site:

As it adsorbs waste products, Purigen® will change color from a pale blonde to a dark brown, almost black. Once it is exhausted, it can be regenerated with a solution of bleach and water.
This is the main reason that many aquarists only use Carbon, Ammo-chip, and other absorption medias when there is an emergency, or when removing medicines - because otherwise the media expires and then starts causing more harm than good.
"To know that we know what we know, and that we do not know what we do not know, that is true knowledge." -Confucius

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Old 10-04-2010, 05:29 PM   #7
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Welcome aboard.
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Old 10-04-2010, 05:34 PM   #8
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I have wondered about the continuing health...

of the other components of the filter--specifically the bio-media stuff. I do clean it, but there is so much crap in the water, I wonder if the pores get plugged.

I do recharge the Purigen--I have several in rotation at any given time. It is really easy to see when it is in need of a bath. However, I do not know how well Purigen works to begin with. Who has time to test these things? Not me. I know it will do more than carbon, and it seems to help keep N-compounds down, but who knows for sure.

Originally Posted by Vircomore View Post
You may want to check on the quality of your Seachem Purigen in your filters. Just like other "Impurity Absorbers" - Purigen can "fill up" and then once it does - it will begin leeching by-products of what it's gathered back into the water.
- because otherwise the media expires and then starts causing more harm than good.

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