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Hi i've got a low ph issue and was wondering the best way to tackle it. My water comes out the tap around 6.8-7 and when I set up the tank about 4 months ago it rose to about 7.4 then settled to 6.6. Well I tested over the last few weeks (after a bristlenose died for seeminly no reason)and it read 6.2 which is the lowest my test kit goes too. I had a suspicion it was lower so bought a low range kit and it puts my ph at 5.5. I don't know about the hardness as I don't have a kit but suspect it is more soft than hard.
Know I have heard that crushed coral can raise/stabilise ph what sort of ratios are required?
I have also heard that you can use bicarb soda to increase the ph what are the ratios for this? and how long does its effect last?
I would like to keep the water slightly acidic for the tetras (rummys and cardinals)


My tank is 40 gallon and stocked with some tetras 2 rams and 2 drawf gourami it is planted and over filted with a canister rated at 1000lph. All common parameters are ok
0ammonia, 0 nitrite and 10 nitrates.

Whats your Carbonate Hardness? Its height affects whether or not your pH moves... Chances are your pH got to 6.6 and then your KH got to 300 and now your pH wont move. A way to bring it down will be water changes of 20-25% every other day, or pumping carbon dioxide into the water until it lowers... (i would just do water changes). Change your water or add CO2 until it is lowered to 100 that should allow you to add a chemical that raises pH until the desired pH and then only change water once a week and your KH will raise making your water maintain the pH your rose it to.

I've gone and bought a test kit and have since found out my water is very soft 1 dKH so I'm thinking I might need something to add buffers, am I right?

would it be best to use something like bicarb or add crushed coral

I will pobably use bicarb first as I have some in the cupboard how long should i wait to test the water after adding it?
thanks to anyone that replies

If you have South American fishes in your aquarium, I would NOT rush into raising the pH too much ... don't forget that most of these fishes hail from soft, acidic waters in the wild, and although a pH of 5.5 might be a tad extreme for some (though if you're breeding Discus it's just fine), it probably wasn't the primary cause of death of your Bristlenose.

The question I have to ask is this. When did the aquarium last receive a water change and gravel vac?

If your tap water is very soft and acidic naturally (and thus well suited for keeping and breeding a whole brace of South American fishes), then frequent water changes and gravel vacs are a must. Even a modest amount of decomposing mulm left in the gravel will precipitate a pH drop. Increasing the hardness of your water is a bad idea because most South American fishes prefer soft, mineral deficient water. In fact, if you have Rummy Nosed Tetras, the WORST thing you can do is add anything containing Calcium Carbonate to the water, as it has been determined by scientific experiment that Rummies stop breeding if subject to increased concentrations of dissolved Calcium ions in the water. TFH magazine covered this little facet of Rummy maintenance in a recent article on fish breeding.

Furthermore, if you have low carbonate hardness, this is ideal for breeding Glowlight Tetras. Glowlight Tetras can be persuaded to spawn in aquarium water ranging in carbonate hardness from zero up to about 8 degrees KH, but the fry will NOT survive if the carbonate hardness is above a lowly 1 degree KH! Glowlight fry are extremely sensitive to carbonate hardness in the first 7 days of life, and have to be migrated slowly to increasing carbonate hardness levels. Of course, as you've found out, keeping pH stable in water with such low carbonate hardness values is something of a work of art, but I would NOT rush out and start adding chemicals to your water without addressing several other important issues first. The principal one being how heavily stocked are you?

Soft, acidic water, while it is ideal for South American fishes hailing from Amazonian biotopes (and very good for a range of other fishes from rainforest habitats too, such as some West African fishes, and quite a few fishes from Asia) requires careful attention to stocking levels. Stock too heavily and you're looking at a pH crash in fairly short order. Light stocking is advisable, with small incremental changes in the stocking to find the 'critical point' beyond which the setup ceases to be stable.

The second question (which I covered earlier) is how often do you gravel vac the aquarium? Frequent gravel vacs to remove mulm from the substrate are highly advisable in soft water setups, precisely because the mulm, when it is being decomposed by substrate bacteria, yields a host of acidic compounds. These are eventually metabolised to something less troublesome, but the trick is to keep the source of these compounds at a low level to keep a pH crash at bay. It's not overdoing it to gravel vac twice a week, especially if you're well stocked. Check especially for 'dead spots' that are becoming dark in appearance - these are areas where anaerobic bacteria will manufacture acidic and in some cases toxic metabolic by products - the worst being Hydrogen Sulphide, an extremely water soluble gas that is as toxic to fishes as Cyanide! For that matter, it's similarly toxic to humans too - I have some interesting personal experience of incipient respiratory arrest from an industrial pollution incident invoving this gas near my home ...

Next question - is your aquarium planted? Aquaria with lush plant growths tend to be more stable than those without. Not least because the plants, once established, carry oxygen to the substrate in which they are planted, and thus contribute to the efficiency of the substrate bacteria in their processing of nitrogenous wastes. Plants will, once established, help to oxygenate the substrate via the roots, and perform a whole brace of other operations as part of their own metabolic processes that help to keep your water reasonably stable.

If after covering these bases, you have problems maintaining stability even with light stocking and scrupulous attention to substrate cleanliness, only then should you consider a chemical adjustment. Any adjustment you make should be gradual, because a LARGE and SUDDEN change in water chemistry parameters will stress your fishes much more than their current conditions!

Incidentally, you would be surprised at the pH levels found in the natural home waters of some South American fishes - the Rio Negro, for example, which is the river in which Cardinal Tetras breed, returns pH values as low as 4.0 at some times of the year ... likewise, there are some African fishes that live in waters whose natural pH is very low - Barbus hulstaerti, the Butterfly Barb, is also known as the Vinegar Barb because it's home waters are at a pH of 4.8.


Panda Catfish fan and keeper/breeder since Christmas 2002

thanks to all who posted and the big one from Calilasseia
my tank is quite heavely planted
water change 20% and gravel vac 2wkly (two chnges and cleans in last week while trying to improve the tank)
am i right in that I can raise the hardness without much of a ph shift and then the tank will be more stable. I'd like it to remain acidic but not that low.

I have since added some bicarb and it raised the ph but has not changed the carbonate hardness, is this normal?

thanks

Oh now I have a sick cory check hospital post if you can help

2 rams and 2 drawf gourami 3 corys,5 cardinals 3 rummynose in planted 40 gallon