Tropical Fish pH Question

MicroE

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Are there any tropical fish experts on CPF?
I have a 20-gallon (76-litre) freshwater tank. I check the pH at least twice each week using an electronic gauge.
The pH is always low (below 7). It typically drops to 6.5 in two days and will keep dropping if I don't correct it.
It once drifted down to 4.65 and the fish were near death.

Why does the pH always drop? How can I stop this?
The tank has plenty of air and water circulation and a large canister filter. It is well established (over 2 years in service). It is not overcrowded. There are only 7 fish: a pleco (armored catfish), two tiger barbs, and 4 pearl gouramis.
Is it the food? I give the barbs and gouramis Tetra flakes and the pleco gets algae disks.
I would appreciate any help.---Marc
 

javafool

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I used to raise tropical fish and never concerned myself with pH. The fish will pretty much adapt.

The most important part to keeping a healthy tank was to control the temperature, feed them good food, have good filtration, and change (replace) at least 1/3 of the water in the tank weekly. This is very important to keeping a good tank that most people totally neglect.

Unplug the heater.
Drain 1/3 to 1/2 of the water from the tank and dump it.
Add fresh, chlorine free water that is a few degrees warmer than the normal water temperature, NEVER colder.
Plug in the heater and watch all those happy fish swim and smile.

Good luck,
Terry
 

asdalton

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Intervention to control pH is rarely necessary, but 4.65 is far too low. I suspect that something else is going wrong here. One thing that can cause large pH swings--particularly pH drops--is poorly buffered water. In this situation, any CO2 produced by fish and bacteria will cause the pH to fall.

The buffering capacity of water is mainly a function of the presence of weak bases such as carbonate and bicarbonate. These tend to keep the pH on the high side, but more importantly, they make the pH stable and difficult to change. Usually this is a good thing. Note that buffering is NOT the same thing as hardness (Ca++ and Mg++ ions); water can be hard and poorly buffered, as well as the opposite.

You should try using limestone-containing rocks or gravel as a long-term solution to pH drops.
 

lymph

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4.65 - That's really quite low. Do you have any real wood in the tank for decoration? Wood could be acidic.

Live plants could help absorb some of the CO2, which makes carbonic acid and lowers pH. When I used to grow caulerpa algae, my pH would get really high.

You might want to try a commercial buffer material. I'm more familiar with the salt-water products of 5 years ago (I've been out of the hobby for a while), but there might be some "blocks" of material that act as a buffer.

I've heard that adding a little crushed coral helps.

Also, how often do you do water changes, and how much do you change?
 

bwaites

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4.65 is crazy low, especially in the short time frame you are talking about.

Something in that tank must have a lot of acid creating compounds of some type.

If you have a local lab that does soil/water sampling, you might take a sample in and see what weak acid is actually forming, and then work from there to determine what is contributing.

Are there any structures in the tank, limestone or sandstone?

How about any sulfur stones or similar?

I recently had a ten gallon tank, with more fish than you are handling, and never had this kind of a problem, and I'm NOT the best at doing water changes.

My bet is that there is something in the tank or filter that is combining with the water and causing the weak acid formation, and it isn't the fish!

Bill
 

MicroE

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There is no wood in the tank, only a commercially-manufactured gravel. I suppose that the gravel could be the problem, but that seems rather far-fetched.
Adding limestone sounds like a good idea to add buffering capacity. I am using water from the tap, so the buffering capacity is totally unknown.
I used to use water from our water-purification system when doing water changes, but I was told that the fish need the Ca and Mg in the water, so now I just use it from the tap (after removing the chlorine, of course).
 

bwaites

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Micro,

When you clean the tank and filter is there a sulfury smell?

Some cheap filters trap sulfur and under the right(wrong?) cicumstances you might develop a mild sulfuric acid. Once again, a relatively inexpensive water analysis by a lab would be able to check that.

Bill
 

MicroE

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There is no sulfur type of smell. I suppose I could get a water analysis done to determine the type of acid, but I'm really cheap (unless you're talking about flashlights, of course).
 

koala

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MicroE - if your suspecting your tap water, go to your local fish shops, talk to them and ask them about the water quality in your area. Go to a few shops and collect that info. Most of the time your tap water quality will be similiar to theirs unless you are using rainwater.

Is your tank new? Some crazy tank manufacturers use unsafe sealant to glue that their tank, then stuff leech slowly in to the water.

ph4 is really acidic, are you sure you or your kids didn't feed coke to your fishes? accidentally? /ubbthreads/images/graemlins/grin.gif

We don't know what you have/put in the tank. Do you have CO2 injection? Probably not. My last recommendation is to remove items in your tank one by one until your ph settle. Leave the filter there, your fish need it.
 

BB

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Perhaps you may also try and purchase a cheap chemical PH tester/strip test set and confirm your electronic PH test results as accurate.

Also, you can get a multiple test strip that checks ~5 different chemical/hardness levels. They are not that cheap--but I only used a 1/2 dozen until I was confident in the general tank chemistry (my kid's fish at In-Law's house--not expensive fish).

If the fish store does it right, you will end-up spending more on chemicals, test strips, replacement filters, light fixtures, etc. than you did for the original tank and fish (and replacement fish) /ubbthreads/images/graemlins/wink.gif

-Bill
 

MicroE

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Everybody wants to know what the decorations are in the tank. Here goes: Three plastic plants and the gravel. That's it, nothing to leach or react (unless it is the gravel).
The tank has been set up for 2+ years and was made by Hartz.
The pH meter is accurate. I personally calibrated it using buffers at 4.0, 7.0 and 10.0. It is more accurate than the pH meter in our electroplating department /ubbthreads/images/graemlins/smile.gif.
I did a 1/3 water change yesterday and another 1/3 today. The pH is now 7.51. The local fish stores have been no help at all and that's why I posed the question here on CPF.
The local tap water has a pH around 8 and its quality changes with every rainstorm. Now I know why I drink bottled water at work!
 

javafool

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Good! 8 sounds about right for the local tap water. It will be interesting to see if it changes over the next few days. Please keep us posted because I am very interested.

Terry
 

MoonRise

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Eliminate things one by one and figure out what the cause of the pH drop is.

One wacky thought just occurred to me. If an electric device (heater typically) has malfunctioned such that it is causing electrolysis to occur (electrical breakdown of water into H2 and O2), hydrogen ions would be produced and cause the acidic condition.

Either that or someone is dumping cola soda into the tank daily. /ubbthreads/images/graemlins/eek.gif

To rule out the food as the problem, take three clean plastic five gallon pails and fill them with tap water. Check the pH on all three and make sure they are all the same. Put them into the same room as the fish tank if possible. Add some Tetra Flakes to one pail, add some algae disks to a different pail, and leave one pail untouched as a control. Check the pH in the pails and the tank once or twice a day and log the results.

Maybe your fish are full of p#$s and vinegar? Vinegar is acidic. /ubbthreads/images/graemlins/crackup.gif
 

mahoney

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Some questions that came to mind.

Before I added limestone to a tank with these symptoms, I would look for decaying organic material.

Do you have an undergravel filter or is the gravel just sitting on the tank bottom? How deep is it? Do you ever vacumn the gravel?

My water comes out of the tap hard as a rock, so I never test for PH in my tanks anymore, but it sounds like your water has little buffering capacity, as has been mentioned, and over time the accumulation of waste in a tank will push down PH. I have had problems with tanks that had gravel without a UG filter, unless the fish load was very low, or the gravel layer was very thin (<3/4")and well vacumned at each water change. If you poke a finger into the gravel and sulfer smelling gas bubbles up, or "dirt" swirls up, the gravel is likely your problem.

How often do you clean/rinse the biological filter material in your canister filter. That's another place where organic material can build up. I rinse all my bio filtering materials in the siphoned out tank water during each water change.

What species is your pleco? All species tend to be heavy eaters (and poopers) and many species will outgrow a 20 gallon tank given one to three years growth. With the gouramis and barbs, I would say your tank was at a comfortable capacity depending on the size of the pleco, but not understocked. Tank capacity is more about the size and mass of the fish than the quantity or length of the fish. Try feeding your pleco zuchini, peas, or romaine lettuce. Some brands of algae wafers contain a fair amount of protein in the form of fish or meat products that can really add to the load on the filters. IMO, they are a good supplement or treat a couple of times a week, but are pretty "rich" as a steady diet for a pleco.

Some real plants will help with the situation, even if it's just duckweed at the top of the tank. Without knowing which species of pleco you have, I wouldn't recommend any submerged plants but Java moss or Java fern as some plecos will consider any other plants a light snack.
 

MicroE

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Mahoney---Wow! That sure is a lot to think about. I do have an undergravel filter in the tank. It is suctioned by a powerhead and really acts like a circulating loop rather than a filter.
Even so, there is a lot of "dirt" in the gravel. I always use a siphon to pull out the dirt when I do a water change, but I probably don't do water changes as often as I should.
The plecos are REALLY big poopers. We hava one in the house tank that is full grown and I swear that that fish produces his body weight in waste every other day!
On Monday I will strip down the canister filter, remove any organic soup in it and change the carbon. The tank is in my office at work.
I have not put plants in the tank because of the pleco. I have heard that they will eat all plants in the tank.
BTW, he is black with light brown spots---I have no idea of the species---Plecus Cheapus would be my guess.
---Marc
 

asdalton

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After reading more of these posts, I now think that partial water changes may be the simple solution to your problem. No matter how good your filter is, partial water changes are still necessary. The major reason for this is that no aquarium filtration system can support all of the parts of the carbon cycle and nitrogen cycle that occur in nature.

The long-term result is an accumulation of nitrate and carbon dioxide (with the acidity that accompanies the latter). Nitrate (not the poisonous nitrite) is often considered non-toxic, but it can rise to toxic concentrations if it is allowed to accumulate indefinitely.

Partial water changes--say, 25% every two weeks at the minimum--will remove acidity and replenish the buffering capacity of the aquarium water. Since you have an undergravel filter, you should also vacuum the gravel about once a month during the water change. Removing waste from the gravel takes carbon out of the tank, depriving the heterotrophic bacteria of nutrients that they use to grow and produce CO2.

I will say some things about undergravel filters in another post.
 

javafool

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Evcellent information Andrew. When I bread Anglefish (all work and almost no profit) and several other egg layers I used bare bottom tanks for my breeding tanks. As the fish grew larger and the tanks became more and more crowded. I was changing at least 50% of the water in the breading tanks daily. On the weekends I just changed about 1/3 to 1/2 of the water in my show tanks while doing the other tanks.

I did always drain the show tanks using a gravel cleaner and was very careful not to stir the gravel contents into the water. 25% every other week should be quite adequate and I agree it should solve the problem. The first gravel cleaning may go slowly so you may only want to clean the gravel in half or 1/3 of the tank the first week and do the rest during subsequent water changes. Over the next few weeks I expect Marc to see a favorable change in his aquarium and the fish.

Terry
 

MicroE

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Update of 5 January.
Three weeks ago I began regular vacuuming of the gravel and have performed 3 water changes (about 1/3 of the tank on each change).
The pH seems to be holding near 6.7
I believe that all of the organic matter (uneaten food and fish waste) must be the source of the acid. It is this bacterial "soup" that is causing the low pH problem.
Going forward I will feed them less, not let other people over-feed them and perform periodic water changes.
Thank you all for your help.---Marc
 
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