TDS dropping instead of rising? - The Planted Tank Forum

 
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post #1 of 7 (permalink) Old 05-13-2013, 03:48 AM Thread Starter
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TDS dropping instead of rising?

Is it possible for the TDS to drop in a shrimp tank without water changes? I measured the TDS of my tank last week and it read at 320 PPM. I measured it a few minutes ago and it's now 280. The GH is at 9 degrees and the KH is at 4 degrees. I didn't do a water change and I've been doing top-offs with dechlorinated tap water every few days because of evaporation. The last time I did a water change was over a month ago. The flora is a bunch of random mosses, hygros, java ferns, crypts, and a mix of floaters that cover the top of the tank. The fauna include: Red rilis, Blue Velvets, Caridina babaulti, assorted snails, and horned nerites. I always have berried females and I see babies swimming all over the tank and on the front glass so everybody seems happy. Feeding is done every 2-3 days with a rotation of algae wafers, Repashy foods, Shirakura shrimp food, barley pellets, and blanched organic baby spinach or kale. The substrate is black diamond blasting sand mixed with a little bit of crushed coral. The only hardscape is one rock and a small piece of Malaysian driftwood covered in mosses and java fern.

Anyone have any ideas as to why my TDS would be dropping?

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post #2 of 7 (permalink) Old 05-13-2013, 03:57 AM
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You might have had something in the water column that you picked up with your TDS pen, that your filter has since cleared from your water. Filter carbon will do it.
I wouldn't worry about it.
The other possibility is that your TDS pen is giving you inaccurate measurements.

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post #3 of 7 (permalink) Old 05-13-2013, 04:03 AM Thread Starter
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Thanks for the reply. I don't use activated carbon in this tank. I only use a sponger filter and Hagen Elite mini filter filled with bio media for circulation.

I guess I'll try calibrating my TDS pen tomorrow. Now I need to figure out where I put the calibration fluid that came with the TDS pen.

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post #4 of 7 (permalink) Old 05-13-2013, 12:51 PM
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Since tap water Params often fluctuate the TDS could have dropped in your tap and your top offs have been lowering it.
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post #5 of 7 (permalink) Old 05-13-2013, 02:25 PM
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bioassimilation from your plants. if you have any fast growers (floaters in particular, like hornwort, or duckweed) they will be sucking fertz out of the water, lowering your TDS.
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post #6 of 7 (permalink) Old 05-13-2013, 04:29 PM
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can i ask why you have blue velvets in with rili? as for tds if u use powder foods that might do it.
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post #7 of 7 (permalink) Old 05-14-2013, 03:00 AM Thread Starter
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Quote:
Originally Posted by ravensgate View Post
Since tap water Params often fluctuate the TDS could have dropped in your tap and your top offs have been lowering it.
My tap is usually in the 45-50 PPM range. Though I don't think doing top-offs with tap would lower the TDS.

Quote:
Originally Posted by wicca27 View Post
can i ask why you have blue velvets in with rili? as for tds if u use powder foods that might do it.
I wanted to see if I could get more blue midsections in my red rilis. So far it's been going alright. I've gotten a mix of red rilis, blue rilis, some blue velvets, and oddly colored rilis in the progeny (some greys and a rili with orange spots). Though most of my reds looks a bit bluer in the midsection. I don't selectively cull though since catching them in a heavily planted tank is near impossible. So I'm satisfied with what I end up with.

I don't use powdered foods and I don't understand how using them would lower the TDS over time. If anything, they would raise the TDS.

Quote:
Originally Posted by @marko@ View Post
bioassimilation from your plants. if you have any fast growers (floaters in particular, like hornwort, or duckweed) they will be sucking fertz out of the water, lowering your TDS.
Most likely. My floater mix would cover the entire top of the tank if the bubbles from the sponge filter didn't keep them engulfing that tank corner.

Anyways, I found the calibration fluid. However it's at 1382 PPM, too high to calibrate with since you're supposed to calibrate your TDS meters with an NaCl solution that has a TDS in the same range you're normally used to seeing. I'll probably go to the local hydroponics center on my day off and see if they have any 326 PPM calibration solution.

Here's a pic of the tank:



It's supposed to be a lot darker but the phone on my camera automatically bumped up the brightness.

And here's the mass of floaters.



It's a mix of giant duckweed, frogbit, DWL, and a bit of hygroryza that's slowly being smothered. I'll probably replace most of the floaters with some antler fern I got locally from another member. Also, Don't mind the aphids. They're pretty much impossible to get rid of.

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