Need help understanding TDS

Crimson_687

I understand that TDS- total dissolved solids- cannot tell me what those solids are and can be either organic or mineral content. What’s concerning me is the large TDS difference between my two tanks and how quickly the TDS of my 10gallon shrimp tank changes. The TDS difference seems to affect my cherry shrimp as well. As far as I know, the tds of our tap water has not changed.

My 36gal community tank has a TDS of 360-390, usually reading at 380. This number is constant. In this tank, the cherry shrimp I added grow larger and females are more readily saddled. The pH, ammonia, nitrite, nitrate of this tank are identical to the 10gal. Both are on the same tap water and receive the same amount of seachem flourish and prime relative to volume. This tank gets a 30-40% water change every 1.5-2 weeks. Sometimes I will do a 50% if it has been 3 weeks.

In the 10gal, TDS started at 380-400 within a month of set up, but is readily increasing. TDS read 400-460, then 480-520, and now 540-580, currently reads 560. This tank gets a 20-30% water change every 1-1.5 weeks. In this tank, cherry shrimp are smaller and I do not see them saddle as often (but also breed faster as there are more males and it is easier for them to find females). Shrimp in both tanks are very active, though more so in the 10gal as they feel more comfortable without high-activity of the community fish. This tank also has more plants. The chain sword and ludwigia grow readily.

I’m not sure what’s causing the difference, but I hope to understand it and stabilize the tds.
 

LowConductivity

I’d wager the difference probably has something to do with evaporation and not changing enough water to combat the accumulation of solids
 
Upvote 0

Crimson_687

I’d wager the difference probably has something to do with evaporation and not changing enough water to combat the accumulation of solids
If this was the case, wouldn’t both tanks have steady increase? Both tanks evaporate and the larger tank has been setup for longer
 
Upvote 0

GlennO

Interesting, it's the same thing for me, my 7 gal shrimp only tank has a higher TDS than my other larger tanks that also contain fish. It could be due to a couple of things. I have a couple of small Seiryu stones in there that might be contributing. Also, I believe that TDS measures dissolved organics as well as inorganics, so perhaps even the leaf matter that I add to much smaller volume of the shrimp tank contributes. I also do smaller water changes, 25% weekly compared to 30%-50% for my other tanks.
 
Upvote 0

Cherryshrimp420

I understand that TDS- total dissolved solids- cannot tell me what those solids are and can be either organic or mineral content. What’s concerning me is the large TDS difference between my two tanks and how quickly the TDS of my 10gallon shrimp tank changes. The TDS difference seems to affect my cherry shrimp as well. As far as I know, the tds of our tap water has not changed.

My 36gal community tank has a TDS of 360-390, usually reading at 380. This number is constant. In this tank, the cherry shrimp I added grow larger and females are more readily saddled. The pH, ammonia, nitrite, nitrate of this tank are identical to the 10gal. Both are on the same tap water and receive the same amount of seachem flourish and prime relative to volume. This tank gets a 30-40% water change every 1.5-2 weeks. Sometimes I will do a 50% if it has been 3 weeks.

In the 10gal, TDS started at 380-400 within a month of set up, but is readily increasing. TDS read 400-460, then 480-520, and now 540-580, currently reads 560. This tank gets a 20-30% water change every 1-1.5 weeks. In this tank, cherry shrimp are smaller and I do not see them saddle as often (but also breed faster as there are more males and it is easier for them to find females). Shrimp in both tanks are very active, though more so in the 10gal as they feel more comfortable without high-activity of the community fish. This tank also has more plants. The chain sword and ludwigia grow readily.

I’m not sure what’s causing the difference, but I hope to understand it and stabilize the tds.

The same amount of food will result in a bigger TDS change in a smaller tank than a larger tank, so it's easy to have TDS climb quickly in smaller tanks. You just gotta do more water changes
 
Upvote 0

Crimson_687

It’s probably food and stones then. I give powdered foods to the shrimp in that tank. Now that the tank is older, there’s probably more biofilm and they’re relying less on supplements. I suspect they may not like the taste of moringa powder either as they’ve been less excited for powdered food since I added moringa. Unless the snails have been eating it that probably goes uneaten
The most recent (and biggest) tds change occurred around the same time I added new ohko stone to the tank.
Do you know which mineral in particular ohko/dragon stone will release? My tap already has around 60ppm calcium so I’m concerned that the calcium content will become too high for the shrimp to shed properly
 
Upvote 0

GlennO

My understanding is that dragon stone doesn't affect hardness, unlike Seiryu type stone which contains calcite seams.
 
Upvote 0

Convoluted77

Glenn is correct. True ohko dragon stone is inert and will not effect water params but there's plenty of "dragon stone" out there that isn't true or has calcium deposits or whatev in it. If you have any leftover stone or want to remove a piece from your tank you can do a vinegar test on it to see if there's a reaction or let some sit some sit in a small container of water and see if the tds rises over time.
 
Upvote 0

FishareFriends6

I hate TDS and it is a head destroyer trying to fully figure out. Rocks leach calcium, apart from dragon stone; as already said by someone else, due to being clay based.

Evaporation will allow the minerals in the water to concentrate more, than if they had more water to dilute them with. You would need a RO system to reduce the TDS in the tank. If you add tap water to top it up, you are essentially increasing the amount of minerals already in the concentrated mix, resulting in higher and higher TDS.

You need a GH/KH test kit, to figure out what both your hardness parameters are. When I first got my TDS meter, I lived by it (German Blue Rams like soft water) but then realised it’s just a nice general check for when to do water changes, not actually do anything else with. You could get your calcium to 0 and the TDS meter could still say 739… which to me means it’s pretty poop unless you know what you’re looking for.

Also, even though to your eyes the tanks are ‘identical’, they are both closed seperate systems. Both may act similar but will be different.
 
Upvote 0

Linda1234

Do both tanks have substrate? Also most tds meters are a bit of an approx to actual tds since they measure conductivity and not actual tds.
 
Upvote 0

Crimson_687

Do both tanks have substrate? Also most tds meters are a bit of an approx to actual tds since they measure conductivity and not actual tds.
Yes both tanks have the same substrate.
I hate TDS and it is a head destroyer trying to fully figure out. Rocks leach calcium, apart from dragon stone; as already said by someone else, due to being clay based.

Evaporation will allow the minerals in the water to concentrate more, than if they had more water to dilute them with. You would need a RO system to reduce the TDS in the tank. If you add tap water to top it up, you are essentially increasing the amount of minerals already in the concentrated mix, resulting in higher and higher TDS.

You need a GH/KH test kit, to figure out what both your hardness parameters are. When I first got my TDS meter, I lived by it (German Blue Rams like soft water) but then realised it’s just a nice general check for when to do water changes, not actually do anything else with. You could get your calcium to 0 and the TDS meter could still say 739… which to me means it’s pretty poop unless you know what you’re looking for.

Also, even though to your eyes the tanks are ‘identical’, they are both closed seperate systems. Both may act similar but will be different.
I know that dragon stone is inert though it’s possible I missed some sediment pockets while cleaning. GH kh off the tap is stable but I don’t have a kit. There’s an LFS that tests gH kh so I will bring a tank sample next time I go. If the TDS is mineral content I’ll do a wc with distilled water, but I want to be sure it isn’t something else

Edit: TDS read 560 today
 
Upvote 0

Cherryshrimp420

Yes both tanks have the same substrate.

I know that dragon stone is inert though it’s possible I missed some sediment pockets while cleaning. GH kh off the tap is stable but I don’t have a kit. There’s an LFS that tests gH kh so I will bring a tank sample next time I go. If the TDS is mineral content I’ll do a wc with distilled water, but I want to be sure it isn’t something else

Edit: TDS read 560 today

Everything adds to TDS. Rocks, substrate, food, poop, everything... You don't have to go out of your way to find what's in it. Just do a water change when it is high.

560 TDS is very high for shrimp, I suggest bringing it down to 300s or your colony will slowly die out.
 
Upvote 0

MacZ

I’ll do a wc with distilled water

Always brings TDS and EC down. It dilutes everything equally. And please don't change more than 25% at once with straight distilled or RO.
 
Upvote 0

Linda1234

Something in the tank is leaching. I have several tanks setup for multiple years and they never drift by more than 10% tds. Evaporation isn't causing your problem.
 
Upvote 0

Crimson_687

Got the water tested today for gH kH:

36 gal: 12 gH, 5 kH
10 gal: 17 gH, 6.5 kH
Tap: 13 gH, 8 kH

I also ordered my own test kit for gH kH so I can continue to monitor it. I put a piece of the dragon stone in a separate container and will test parameters to see if it’s leaching
 
Upvote 0

MacZ

I also ordered my own test kit for gH kH so I can continue to monitor it. I put a piece of the dragon stone in a separate container and will test parameters to see if it’s leaching

You should, because though the numbers are not impossible the difference between GH and KH usually is less than you have in your tanks. Your tap looks likely, though.
 
Upvote 0

Crimson_687

So I tested it myself and got different results,

kH began to turn color on the 4th drop and became bright yellow on the 5th drop, so 4.5. gH began to turn on the 14th drop and became a bright green on the 15th drop, so 14.5. I don’t think it could have dropped this much in just 2 days and a 20% wc with tap. How would I know if my kit was faulty? It expires 2024. The LFS and myself used the API liquid test. The samples I took to the LFS were in bags I saved from fish I brought home so I don’t think it contaminated the sample.
 
Upvote 0

MacZ

That's not a bad result. And I think there is always a bit of room. I'd rather expect their testkit a bit off, but but all results are within the accuracy of a home testkit.
 
Upvote 0

Linda1234

I'm not sure i understand what you are saying. My water test consistently with the liquid api for the past 3 years. I also don't see much drift in both low tech and high tech tanks with regards to gh and kh; though tds has inched up in one tank from 120 to 140 over 3 years.

That's not a bad result. And I think there is always a bit of room. I'd rather expect their testkit a bit off, but but all results are within the accuracy of a home testkit.
 
Upvote 0

MacZ

I was just comparing the accuracy of the results of the OP and the tests at the store as they were a bit apart. It can be a bit off between kits even from the same manufacturer.
 
Upvote 0

Crimson_687

The TDS seems to hang at 540 now, hitting 560 only before a WC. KH read the same, 4.5, but gH read a bit lower, about 13-13.5. I think that gH spiked when I added the rocks, either from the rocks themselves or because the substrate shifted, and now gH will crawl down again. If it was the rocks, it seems to have been immediate so I don’t think the rock is leeching. I’ll start doing 5% RO WCs every month to combat evaporation as well and do regular WCs more often
 
Upvote 0

Similar Aquarium Threads

Replies
3
Views
228
awilkinson871
  • Question
Replies
9
Views
316
richiep
Replies
5
Views
2K
Jayhere
Replies
2
Views
170
Pfrozen
Replies
8
Views
239
ProudPapa

Latest Aquarium Threads

Top Bottom