The Planted Tank Forum banner
1 - 3 of 3 Posts

·
Registered
Joined
·
374 Posts
Hi @Rosalaine,

Work out your total dGH + dKH then multiply by 18 to get the respective TDS (ppm). So you said about 8 dGH in the tank so if the KH is 0 then (8+0) x 18 = 144 ppm. So you know that 144ppm of your TDS is GH and KH and the rest (about 100ppm) is something else. Prevailing wisdom seems to be that caradina shrimp like "clean" water, i.e. a TDS that is not too much above the GH+KH ppm total, which would suggest that your tank water has a "high" TDS. I can't say whether or not these recommendations are correct or not for your shrimp as I've not (yet!) kept them myself. But if everything else seems spot on and they aren't quite thriving as you would like then maybe reducing the TDS is something to consider?

Before you do though, buy some calibration fluid and calibrate your TDS meters. Don't rely on the factory calibration which can be off. Reading 0ppm for distilled water is also not an indication of accuracy of readings higher up. I wouldn't do anything until you are sure sure that your tank TDS readings are correct. (From what you described, they don't seem a million miles off though given the TDS of your remineralised distilled water).

Lowering TDS in a shrimp tank is hard because big water changes are a shock for the shrimp. So a couple of suggestions:

1) add a bag of Purigen to the filter and see if this brings down the TDS.

2) take out a small amount of tank water at a time a replace with distilled water. Repeat multiple times over the course of a week to bring slowly down the TDS (keeping an eye on your GH and stopping when it gets to your preferred level).

3) Try this:

But do make sure you are completely confident in your TDS readings before doing anything (i.e. buy some calibration solution for $9):
https://www.amazon.com/gp/product/B001VE99X8

Regards, James =]
 

·
Registered
Joined
·
374 Posts
Great, let us know how you get on!

I used my RODI today and found that has a slightly higher PH than the distilled - 6.4-6.6 for the RODI as opposed to the <6.0 for the distilled. I'll likely start using that to bump the PH a bit. It reads with 0 TDS as well.
Note that pH readings of distilled and RO water and pretty much meaningless as there is no buffering (KH). Both distilled and RO are pretty much a blank slate with regards to Ph; without any KH the pH can very easily be affected by the additional of anything into the water. As soon as either water hits your tank, has anything added (e.g. minerals), then the pH will change accordingly.

Happy shrimp keeping! =]
 

·
Registered
Joined
·
374 Posts
The TDS meters should be calibrated using a tiny little screw in the back. There should be a hole where you can insert said tiny screwdriver to change the readings.
New HM Digital models are electronically calibrated via the buttons on the front; much simpler and more precise!

The calibration solution will let me know if my $20 meter is any good! You can't really go cheap on a pH meter as cheap pH meters tend to be inaccurate, some wildly so. I'm hoping that with TDS you can go cheap, we'll see.
My experience with cheap meters is that you might get lucky with a good one that is accurate, or it might be miles off. But even with the 'good' ones I'm not convinced about long term repeatability and consistency of the calibration. But once you have a pot of calibration fluid, you're sorted so long as you regularly check the reading is sensible!

Do you have any recommendation for gently bumping the PH of my aquarium? The SaltyShrimp GH+ doesn't seem to alter it at all, and my aquarium itself is at 6.0 or lower currently. I'd like to get it to 6.2-6.4 so I could monitor it's stability a bit better. I'm using fluval stratum for substrate, and from my understanding using anything with KH will start to exhaust the substrate.
Yes - one recommedation: wait! :grin2:

Adding a small amount of KH / buffering will temporarily raise the pH, until the soil absorbs it and the pH goes back down again. You can keep going like that until the buffering is exhausted, but then you have no buffering capacity left which kind of ruins the soil. With time the pH will naturally start to rise and should stablise at the levels you want. But adding KH will just cause the pH to fluctuate which is probably worse for the critters than a stable but slightly low pH would be. So my advice is to do nothing (except don't add too much drift wood, leaves, etc that might reduce the pH further).

Update: With the calibration fluid you linked my TDS meter reads 365, so about 23 ppm more than the fluid indicates it should. I have two of the same type, the other reads 354, so closer at 12 ppm more than the fluid indicates. These meters don't seem like they can be recalibrated, however, so I'm going to shop around for one that can be.
I thoroughly recommend this model:
https://www.amazon.com/HM-Digital-Dissolved-Resolution-Accuracy/dp/B007KDYOMU/

Works great, digital calibration with the buttons on the front (no faffing round with a small screwdriver), reliable, good quality. Cheaper TDS meters do not have temp compensation so, if you're bothered about accuracy (and I'm not sure how much this affects readings across typical aquarium temps), get one with temperature reading and compensation.
 
1 - 3 of 3 Posts
Top