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Quickly rising TDS

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A word of caution. I'm an African cichlid guy. Always have been. I have crazy hard water (one tank, due for a water change, is over 700 TDS), and my fish thank me for it. but, I've recently caught the shrimp bug. I had a 20 gal set up for some cherries and red rili shrimp I had purchased a few months back, but I don't think they loved the hard water. Lost two thirds over the course of 6 months.


I recently re-set up the 20g for some red rili I purchased. Water parameters, after using RO water and Salty Shrimp KH/GH+:


TDS: 168

PH: 7.0



Temp: 74 degrees


But, a week later, my TDS is 198. Is it common for TDS to creep up a bit initially, or do I have something in the tank causing this? The substrate is something I inherited from a used tank I purchased that had plants. Black. I have a couple algae covered rocks in this tank. A little java moss and a few moss balls. An India Almond leaf. I'm hoping to keep the TDS under 200, as that seems ideal for Neos.


Thoughts on this? I am new to RO water. Having Africans and hard water, I NEVER check water parameters, as my fish live long, healthy lives and reproduce constantly. But, I fear this won't be the case with my Neos. If TDS is going to go up 30 each week, that feels like a battle I'm going to lose.



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My guess would be left over fertilizer in the substrate is slowly equalizing with the rest of the aquarium. Especially if they used root tabs at all. It may be difficult to find them, especially if the ferts were extended release.

In my limited experience I would recommend using new substrate of some sort, or just watch your tds and do water changes as it gets close to 220.

Sent from my SM-G935V using Tapatalk

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I pulled the two big rocks out and put them in a bucket of RO water. The TDS in that bucket is going up over the past two days. BUT, the tank that I took the rocks out of is now up to 238. Seems to be going up 10-15 TDS per day. There's hardly any evaporation going on, as it's a fairly tightly sealed tank.

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  • 2 weeks later...

It seems to have, at the very least, slowed way down. I did a 20% water change to get the TDS down a bit, and it seems to be hovering around 180. I'm going to try to continue with small water changes to get the KH/GH back down closer to 3/6. The rocks that I use in my cichlid tanks just don't work in my shrimp tanks. 


Within one week of putting two of these rocks in a bucket with pure RO water, the TDS went from 8 to 46. So whether or not these rocks are THE problem, I'm not yet sure. But, they absolutely contributed. 

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