What is the Best TDS For Guppies?

TDS stands for Total Dissolved Fluids. If you’re a novice fish keeper, ready to set up your first tank, notions like TSD might sound alien. However, this is a critical aspect to grasp since it will impact your guppies’ well-being moving forward.

So, what is TDS, and why is it such an important notion?

The Total Dissolved Fluids are the microparticles that float in the water tank. You get to see them clearer in tanks with dirty water filled with agglutinating particles. They come from a variety of sources, including fish food, fish waste, plants, substrate, algae, etc.

Similar particles are present in the air we breathe, which is where the notion of air pollution comes from. And, yes, they have the same damaging effects on fish as they do on humans.

To prevent any short or long-term health issues, you need to monitor the TDS levels in your tank. The goal is to maintain the level of particles between 400 and 600 ppm (parts per million).

Guppies will generally withstand up to 1000 ppm, but it’s not ideal for their health. So, let’s see how TDS can affect your guppies and how you can prevent TDS accumulation.

How Does TSD Affect Guppies?

The main problem to consider is that oxygen molecules take up space, both in the air we breathe and in the water. High TDS values translate to lower oxygen in the tank, which will affect your guppies immediately.

This is the main reason why foul tank waters will soon become deadly for your guppies. As the TSD levels increase, the oxygen levels decrease, leading to asphyxiation and death.

Several signs are warning of critically low water oxygen levels, including:

  • Guppies gasping for air – If your guppies can’t breathe properly, they tend to swim near the water’s surface. You will see them gasping for air with their mouths wide open, looking for more oxygen. The guppies will also move their gills more violently, trying to pass more water through.
  • Erratic and slow swimming – You might see your guppies swimming in place and showing low levels of energy. Their activity level will drop as they try to preserve their energy to prevent consuming too much oxygen. Guppies may also exhibit abnormal swimming patterns like swimming in place or moving irregularly near the water’s surface.
  • Low appetite – Low appetite isn’t a sign of low oxygen levels in and of itself. It becomes one, however, when paired with the previous 2. If your guppies show low appetite, investigate the matter soon. If it’s not low oxygen at fault, something else might be, like fish illness, parasites, or fish stress.

The effect of TDS shows why regular tank maintenance is key to ensuring a healthy and stable living environment for your guppies. All fish species are sensitive to changes in the oxygen level. In the wild, they have the option to change their location if the water becomes too dirty in the area.

They lack this option when living in captivity, in an enclosed environment. It’s up to you to verify the water’s quality, monitor the TDS levels, and act when the parameters go beyond the safe limit.

Can I Reduce TDS Levels In The Tank Water?

Yes, you can. It’s best to prevent dangerous TDS fluctuations to begin with. Some things you can do to prevent critical TDS accumulation include:

– Avoiding overfeeding

Overfeeding is a problem that many guppy owners will face right from the get-go. Guppies are typically greedy fish, capable of eating more than they need to. They will also respond to feeding even if they’re not particularly hungry; it’s simply their instincts kicking in.

If you feed them too much, food will accumulate in the water and decay with time. This will spike the ammonia levels and create excess TDS via the decaying matter. To solve this problem, only feed your guppies what they can eat in a minute.

Adult guppies also shouldn’t eat more than once or twice per day, at most. I know of many guppy owners who would feed their guppies once per day or even once every other day. This mimics the guppies’ feral feeding pattern where food is scarce and the competition is fierce.

– Performing regular water changes

I advise changing the tank water at least once per week. A 50% change every week is necessary to provide guppies with a clean and healthy environment. Regular water changes will keep the TDS levels in check and provide better water oxygenation.

The frequency of water changes will also depend on the tank’s size and how many fish you have. A 10-gallon tank with 10 guppies will need more frequent water changes since it’s basically overcrowded, leading to fish waste accumulation and accelerated decrease in oxygen levels. The same goes for a 50-gallon tank holding 30+ guppies. However, a 55-gallon tank with 15 guppies doesn’t need as many water changes for obvious reasons.

In this case, the water volume is too high for the 15 guppies, so there won’t be as much waste.

– Performing regular tank maintenance

Regular tank maintenance is just as important as water changes. A dirty tank will show extreme levels of TDS due to fish waste accumulation and algae growth. Dirty tanks also harbor cultures of harmful bacteria that will decrease the oxygen levels and increase ammonia dramatically.

The problem is that most guppy keepers will only perform tank maintenance when the dirt becomes visible. I recommend cleaning your tank at least once per week, depending on its size and how many guppies it holds.

– Avoiding tap water

The problem with regular tap water is that it already contains a higher-than-normal level of TDS. Tap water may be more comfortable to use, but it’s definitely not the healthiest option.

You should also remember that the levels of TDS will generally increase fast in a populated aquarium. Adding tap water to the tank will accelerate the process needlessly.

Fertilizers represent another cause for increased TDS levels. These contain a lot of mineral leftovers, which can boost the TDS levels being the acceptable parameters.


While TDS accumulation is not deadly in and of itself, it can become deadly beyond a certain point.

So long as you take all these precautions, however, and monitor the TDS levels consistently, there should be no danger.

Just make sure to clean your tank regularly and perform the occasional water changes, and your guppies should be fine.

avatar Noah
I’m Noah, chief editor at VIVO Pets and the proud owner of a playful, energetic husky (Max). I’ve been a volunteer at Rex Animal Rescue for over 2 years. I love learning and writing about different animals that can be kept as pets. read more...

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