Need Help With Crystal Red Shrimp Water Change And Top-off

Daniel Nguyen

I have been doing a lot of readings on the internet on how to do a proper water change and top-off in a CRS tank, and still kind of confused about the whole process. So, following are my 4 questions that hopefully will get answers by some shrimp experts .
My shrimp tank's information:
Substrate: Fluval Stratum
TDS: 130-135
pH: 6.4 - 6.6
KH: 0
GH: 5
Temp: 72-74F
Filter: Sponge Filter + Marina S10
Plants: Java Fern

1) Suppose that I have an shrimp tank with ideal water parameters of TDS: 130, KH: 0, and GH: 5. After 2 weeks, the TDS reading is 150, KH: 0, and GH is 5, and I want to do a 20% water change at this point to bring down the TDS level. After siphoning out 20% of the tank, what will be the TDS reading of the tank?

2) For the water that is going to be added back into the tank, I have been told that the water should be exactly the same as the tank water. I don't want the shrimps to get TDS shock after the water change, so should that water that is going to be added into the tank has the TDS of 130 or 150?

3) When the water evaporates from the tank, will the TDS get increased?

4) For top-off, should I top off RO/DI water (mine is 10-20 TDS) or should I top with water that has the same parameters as the tank?


1.) Honestly I'm not sure what it would be after siphoning out 20%, but it would be more. I actually do mine a few degrees lower so that I can actually lower it, eg, if it gets to 140 I'll add back in water with TDS ~132,133. I just add based off what it was before, I use a slower stream out of some airline tubing.
2.) I wouldn't drop it by more than ten, simply because I haven't tried it. I think 130 should be fine, but you don't want to do 150 as the water will get harder and harder and eventually the shell will be too thick for them to molt. I'd say around 140. Mine only goes up about 5 or so a week, so I just bring it down by 5 or so. I think changing it by about 10 is fine.
3.) Yes, similar to how salinity rises in salt water tanks as they evaporate, since the water evaporates and leaves the minerals
4.) I'd just drip it in, depending on the size of the tank at 1-3 drops per second. Use RO/DI.
  • Thread Starter

Daniel Nguyen

Thanks a lot, Rtessy!

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