Ph problem

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aimbdd

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Hi there, I have a small 3 gallon aquarium. The ph is close to 5 in it. I use ro-di water, the substrate is fluvial plant and shrimp stratum, and there is a large piece of driftwood in there, that fills about 25 percent of the tank. The water starts out at 6.5 from the ro unit. Any ideas what I am doing wrong?
 
Welcome to TFF. :hi:

You are not really doing anything wrong. What you see--the lowering of the pH--is perfectly natural. In any aquarium, organics will accumulate. Fish produce these from their food, but organics also occur naturally from other life forms. As the organics accumulate, the breakdown by bacteria produces ammonia and CO2. The CO2 creates carbonic acid in the water, and the pH naturally lowers accordingly.

This can be offset by the carbonate hardness (KH, or Alkalinity) of the water. KH acts as a buffer to prevent pH fluctuation. The stronger/higher the KH, the more buffering capability. With RO water, you have removed all minerals, so the KH along with the GH (general or total hardness, which is primarily the amount of calcium and magnesium) is zero. The organics can thus accumulate and the water will become more acidic.

Wood also adds to the organics, though not all that significantly. The substrate you are using is also contributing to this; from their website:
Helps support neutral to slightly acidic pH - ideal for most plants, tropical fish and shrimp normally kept in planted aquariums.​

No mention is made of fish species; those from very soft water habitats will thrive in this environment. Some shrimp should, but other shrimp might need more mineral. There are ways of doing this, but you haven't asked that so I won't get bogged down. The above hopefully explains the biological process that is occurring.

Byron.
 
Thanks for the answer! Yes the tank is just shrimp. Orange Sakura shrimp. So I got a ph meter, and it’s actually at a ph of 4.5. My test kit from didn’t go that low. I dose the water with Bacter AE Micro Powder for them. The problem with the tap water is high levels of nitrates so I had to start using my ro water. What should I do to buffer the ph higher or add the right minerals back? I had a bunch of shrimp die today, and nitrates nitrites and ammonia are all 0.
Oh and thank you again for your detailed response!
 
Thanks for the answer! Yes the tank is just shrimp. Orange Sakura shrimp. So I got a ph meter, and it’s actually at a ph of 4.5. My test kit from didn’t go that low. I dose the water with Bacter AE Micro Powder for them. The problem with the tap water is high levels of nitrates so I had to start using my ro water. What should I do to buffer the ph higher or add the right minerals back? I had a bunch of shrimp die today, and nitrates nitrites and ammonia are all 0.
Oh and thank you again for your detailed response!

You are welcome. I have next to no experience with shrimp, but many do need some mineral I the water, so this is not surprising that they are dying. I agree not to use tap water high in nitrate, that is only creating another problem.

The easiest thing here would be a calcareous substrate, or using some in a mesh bag in the filter or hanging in the tank. You really don't have any worries with how high the GH and pH might go, within reason obviously, like you could with fish. A sand substrate such as those intended for rift lake cichlids would seem a viable solution. These very slowly dissolve minerals into the water. They last for years and years.

There are also additives for the water, which I have never tried. I don't like adding substances, but here it might not be an issue as presumably they are just minerals and again no fish are present. Can get expensive though, but with small tanks, it could be another option.

I have not had to go down this road, except when I did have a tank of livebearers many years ago, and I used a calcareous substrate in that tank. So others who are dealing with this same issue may have suggestions aside from the two above.
 
The easiest thing here would be a calcareous substrate

I agree with this and use this methode. Mainly we are talking about using calcium Ca) carbonate and magnesium (Mg) carbonate. Both are very similar. They are normally found as rocks (limestone, dolomite; aragonite) or as sea shells or coral.

Ca/Mg carbonates do not dissolve in water with a PH of 7 or higher. However in acid water (PH less than 7) they do. So when the water turns acidic the carbonates react with the acid forming Ca/Mg salts which do not affect PH. In the process of doing this they help push the ph up to neutral (7). Once the acid is gone they don't do anything more and they are essentially just rocks in your tank.

The down side of this is that Ca and Mg will make your water hard. This means the general water hardness test (GH test) will show the hardness increase as the carbonates dissolve. Also any carbonate that dissolves but doesn't react to create a salt will cause the alkalinity of water (KH) to increase. However for a typical aquarium the GH and KH change is typically small and can easily ignored. But Gh and KH changes may not be desirable in some tanks. For example a high tech aquarium with CO2 injection I would not recommend adding carbonates since the high CO2 levels will make the water continuously slightly acidic. Carbonates with CO2 injection can rapidly make the water very hard.

For a basic aquarium all you have to do is add a small amount of carbonate somewhere in the aquarium. carbonate rocks can be uses as decorations or they can be part of the substrate. You can also use them in your filter. the beneficial bacteria will grow on them and help keep the water clean while the water flow insures all the water is treated quickly. The amount need in most cases is small. A single snail shell can take years to dissolve. My planted tanks ph typically stays between 6.5 and 7.2.

The best source of carbonate is dolomite because it is a mix of Ca/Mg. Animals and plants could have problems if the water is mostly calcium or mostly magnesium. Most of the other materials are about 90% calcium. Preferably plants like about 2 parts Ca to 1 part Mg but the ratio doesn't have to be exact. Many GH boosters are 3 or 4 Ca to Mg ratios. Shrimp will do best if the Ca/Mg ratio stays constant at a ratio of 2 to 1 or 4 to 1. Many people with shrimp keep the water GH at about 4 to 6 degrees. However in my experience they will do well at a GH of 2.

In fertilized aquarium calcium and magnesium sulfates or chloride salts are added to to supply the calcium and magnesium to sulfur and chlorides which plants need to grow. They are also used to increase water hardness in aquarium that are stocked with animals that prefer harder water. Plants need a lot of Ca and Mg but less sulfur and chloride. The end result is that as plants consume Ca/Mg excess sulfate and chlorides build up in the water. This forms sulfuric acid and hydrochloric acid. In a small tank I have see my PH go from 7 to 6 in one day. I have recently heard about one person with water at a PH of 3.5 due to CO2 injection and the use of a GH booster. Note some organics are actually weak acids . So as wood, food and dead plants decay the ph can drop due to the creation of organic acids.
 
A single snail shell can take years to dissolve

This shell has been in my tank about 18 months, It also looks cool when my Kuhlis swim thru the eroded bits
6bI5nFU.jpg
 

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