When do I measure my TDS?
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Old 07-03-2013, 02:42 PM   #1
Aquatic Delight
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When do I measure my TDS?


so i am borrowing a TDS meter from work to help me decide what shrimp i can keep. so upon measuring i found that my TDS 358 (i hadn't done a WC in a few weeks.) so did it and got the TDS down to 108. i tested this morning and as expect it had risen, up to 130. so, at what point should i take my measurement and claim that as my TDS? right after a WC, half way between them? right before a WC?


kinda a silly question i'm sure.
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Old 07-03-2013, 02:49 PM   #2
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Dropping TDS from 358 to 108 so quickly is not a good idea. That means you also drastically reduced your water hardness (most likely).

What is your GH?

What is your KH?

You want to maintain a fairly stable TDS. So it should be roughly the same before and after a water change. Hitting that sort of balance is what you're aiming for. More importantly, you want to maintain stability when it comes to GH and KH.
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Old 07-03-2013, 07:47 PM   #3
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Gh was 8 kh was 4 before wc. I'm not home today so o can't retest and be current.

Tds will continue rise though correct?
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Old 07-03-2013, 09:18 PM   #4
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From my understanding TDS will rise as water evaporates and as new substances are introduced to the water column. Solids are left behind when water evaporates thus increasing the concentration of solids to the volume of water and raising your TDS level.
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Old 07-03-2013, 09:33 PM   #5
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You can pick up a good TDS meter on amazon for less than 15 dollars, I would highly recommend having one for the future. You want to measure the TDS of the water you are using for water changes, then the TDS of the water inside the tank. If your TDS was 358 before the water change and 108 after, you must have changed like 50% of the water and the TDS of your tap water must have been close to 0. Are you using RO? The TDS of your tank, if you are doing regular water changes and you do not have too many rocks inside your tank, should not be too much higher than your tap water TDS.

Also it is not a good idea changing the parameters in a tank that quickly, this is what kills fish and shrimp most of the time, so be careful.

TDS will slowly rise over time and daily as water evaporates.
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Old 07-04-2013, 03:40 AM   #6
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Quote:
Originally Posted by somewhatshocked View Post
Dropping TDS from 358 to 108 so quickly is not a good idea. That means you also drastically reduced your water hardness (most likely).

What is your GH?

What is your KH?

You want to maintain a fairly stable TDS. So it should be roughly the same before and after a water change. Hitting that sort of balance is what you're aiming for. More importantly, you want to maintain stability when it comes to GH and KH.
I am not an expert but if drastic dropping is a bad idea I don't think reverse osmosis systems would be so popular in the hobby. I go from 200-0 and dump it for water changes in a day or so whenever I actually get to actually doing the water change. Consistent tank water tds readings would be more important than subtle tds changes. Granted that invertebrates need the hardness I can't say the same for tanks without them. The past several years I have gone with anywhere from 0-25% tap water mixed with RO for my water changes. Even when I use straight RO water, I haven't suffered any losses from doing so.
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Old 07-04-2013, 12:55 PM   #7
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Dropping TDS from 358 to 108 instantaneously means a TON Of hardness was removed. Reduced it more than 3 times. That could lead to molting issues and death. 358 to 108 is not subtle.

People use RO/DI water that is remineralized and they don't alter parameters so quickly. If you must alter parameters, you do so aiming for specific measurements and you do it slowly, over the course of several days or - at a minimum - several hours.
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Old 07-04-2013, 10:36 PM   #8
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RO is popular because the people who use it successfully understand NOT to allow such a big drop all in one go.

To change a tank's mineral composition so drastically they take time, a little today, a little more in a few days, more next week. Over perhaps a month they can take a hard water, high TDS tank down to a fairly soft water tank.

Then use a blend of RO and tap to keep it that way.

DO NOT hold off on water changes, allowing the water chemistry to gradually change, get harder, then hit it with a giant water change that drops everything back to 'perfect'.
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Old 07-05-2013, 02:15 PM   #9
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Quote:
Originally Posted by xdestry View Post
You can pick up a good TDS meter on amazon for less than 15 dollars, I would highly recommend having one for the future. You want to measure the TDS of the water you are using for water changes, then the TDS of the water inside the tank. If your TDS was 358 before the water change and 108 after, you must have changed like 50% of the water and the TDS of your tap water must have been close to 0. Are you using RO? The TDS of your tank, if you are doing regular water changes and you do not have too many rocks inside your tank, should not be too much higher than your tap water TDS.

Also it is not a good idea changing the parameters in a tank that quickly, this is what kills fish and shrimp most of the time, so be careful.

TDS will slowly rise over time and daily as water evaporates.

theres no rocks in it, its just eco-complete, a piece of driftwood, a few mosses, a anubis, and a piece of PVC

i use RO on all of the my tanks.

Quote:
Originally Posted by somewhatshocked View Post
Dropping TDS from 358 to 108 instantaneously means a TON Of hardness was removed. Reduced it more than 3 times. That could lead to molting issues and death. 358 to 108 is not subtle.

People use RO/DI water that is remineralized and they don't alter parameters so quickly. If you must alter parameters, you do so aiming for specific measurements and you do it slowly, over the course of several days or - at a minimum - several hours.
thankfully there is just a few chili rasboras in there keeping bacteria alive. my goal was and is to see where my tank sits naturally, and stick to those parameters. i tend to get lazy and don't want to try to do something i might get lazy and stop doing right.

Quote:
Originally Posted by Diana View Post
RO is popular because the people who use it successfully understand NOT to allow such a big drop all in one go.

To change a tank's mineral composition so drastically they take time, a little today, a little more in a few days, more next week. Over perhaps a month they can take a hard water, high TDS tank down to a fairly soft water tank.

Then use a blend of RO and tap to keep it that way.

DO NOT hold off on water changes, allowing the water chemistry to gradually change, get harder, then hit it with a giant water change that drops everything back to 'perfect'.
I don't normally make that sort of mistake. at that moment i was so focused on how high the TDS was. when i'm doing things right i do my weekly 30% WC on all my tanks, but this tank is new to me and half the time is hidden behind my bathroom door (gotta leave it open because the litter box is in there).

but regardless that tank is back to being on the the WC schedule that the rest of the tanks are on, as this week was 50% water change week.

but since i have mentioned it. 50% wc on a specialty shrimp tank is not a good idea then huh?

the TDS has settled in the 140 range, so i can assume that i have a TDS of 140, and just need to figure out how to keep it in that area? or should i wait another week because the large wc has more than likely really thrown off things?
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Old 07-05-2013, 02:56 PM   #10
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There's a lot to understand if you're to use TDS readings to full advantage.
TDS alone won't be the answer. GH, KH, TDS, NO3, PO4 are what cost vs value I settled on using to monitor my tank water.

TDS readings will include anything conductive in the water which will include most organic compounds as well as the mineral content. Measuring three; GH, KH and TDS prior to and again after the water change helps answer what is actually being changed or removed. While consistent readings may be the ideal, dosing any fert salts throws that idea into a spin.

Pre-maintenance I'll measure TDS then shut off the pumps, clean the glass, trim the plants etc. and do my water change (30-80%). Depending on the size of the system (and what else has me busy) 15-30 minutes later I'll test TDS again, test GH using a chemical titration test then add whatever mineral additions I need for my desired baseline. Normal maintenance generally drops TDS +/-100ppm. (The maximum range of shift recorded here in over 3yrs. is 150ppm pre/post.) Using straight RO (TDS 2.0ppm) for my change water the average drop in hardness is 2-3dH*. (imo) most of the TDS shift I see here is related to organic content.

If you measure TDS first then add trace and macro ferts you'll note a large shift but testing GH find little or no change. (just another thought)

* My systems are all 'softwater' tanks maintained for a 3-5dGH, 0-2dKH mineral range.
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Old 07-05-2013, 03:12 PM   #11
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I'm currently using the api test trips for my KH and GH, with a digital TDS meter. Are there better test kids out there for KH and GH besides the api test strips?
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Old 07-05-2013, 03:13 PM   #12
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Yes. Any liquid KH/GH test kit is better than strips.

Unfortunately, measuring hardness with test strips isn't any better than randomly pulling a number out of a hat.
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Old 07-05-2013, 03:14 PM   #13
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That's what I thought, what brands would you suggest? To be honest I have not looked online for one yet.
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Old 07-05-2013, 03:19 PM   #14
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Any brand you can get. Many people use API but I prefer Sera.
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Old 07-06-2013, 02:32 PM   #15
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Quote:
Originally Posted by wkndracer View Post
There's a lot to understand if you're to use TDS readings to full advantage.
TDS alone won't be the answer. GH, KH, TDS, NO3, PO4 are what cost vs value I settled on using to monitor my tank water.

TDS readings will include anything conductive in the water which will include most organic compounds as well as the mineral content. Measuring three; GH, KH and TDS prior to and again after the water change helps answer what is actually being changed or removed. While consistent readings may be the ideal, dosing any fert salts throws that idea into a spin.

Pre-maintenance I'll measure TDS then shut off the pumps, clean the glass, trim the plants etc. and do my water change (30-80%). Depending on the size of the system (and what else has me busy) 15-30 minutes later I'll test TDS again, test GH using a chemical titration test then add whatever mineral additions I need for my desired baseline. Normal maintenance generally drops TDS +/-100ppm. (The maximum range of shift recorded here in over 3yrs. is 150ppm pre/post.) Using straight RO (TDS 2.0ppm) for my change water the average drop in hardness is 2-3dH*. (imo) most of the TDS shift I see here is related to organic content.

If you measure TDS first then add trace and macro ferts you'll note a large shift but testing GH find little or no change. (just another thought)

* My systems are all 'softwater' tanks maintained for a 3-5dGH, 0-2dKH mineral range.
okay so assuming i continue not to dose ferts, i will need to reminalize my R/o water, or add a small amount of tap to bring the TDS of new water up to old water levels.

i understand nitrates are a concern as they are in any aquarium with livestock.

i've never really concerned myself with phosphate. i have been thinking about learning about it and treating it, as i have a algae problem i haven't been able to stop in my 20l, and the thought has been creeping into my mind that it is a phosphate issue. and not a light or nutrient issue.

would you consider 100ppm to be around the maximum safe drop in TDS?
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