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Discussion Starter · #1 ·
I have a planted with wood 30 long, Eco complete substrate, low tech (excel). I have a corallife regular output light. I use liquid ferts and do a 50% water change very week. I have a wild caught apisto pair with tetras, otos and a bnp.

I bought a couple of toys, TDS and pH meters. I really can't tell the difference in the blue green colors of my pH test kit.

I did a water change today (mixing tap with store bought RO and here were my readings (b1 = bucket 1 of refill, etc.):

Tank before Tap b1 b2 b3 tank 2 hours later
Nitrate 30 -- -- -- -- 20
TDS 305 208 154 120 137 269
pH 6.6 7.3 7 7 7 6.7
GH 9 10 -- -- -- 7
KH 0 4 -- -- -- 2

Something about this just doesn't make any sense to me. I understand the starting high TDS as I was replacing evaporation with tap water. I started using distilled last week. How can my TDS only go down 36 points when i changed 1/2 the water with 150-ish. I did stir up the water a little as I moved a couple of plants, but tried to keep that to a minimum. Does it make sense that my KH = 0. This is only the 2nd time I've used anything but tap water for refills (since I started last January). My tap water hasn't changed much, so what would be lowering it?

Help?
 

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Would be easier for me to understand what you have happening and attempt to help with the information in a different format.

What is you tanks actual water volume filled?
After substrate and scape rocks etc. my 55g holds 43g of water filled.
75g holds 63g, 90g holds 70g.

TDS before a WC, how much water was changed, what is the TDS of the mix (guessing 150ppm) but no clue what the change ratio is, (20%, 50% etc.) and the resulting shift 30 minutes or more after.
Without enough CO2 some plants can break down bicarbonates for the carbon.
 

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Discussion Starter · #3 ·
wkndracer,

Here are the answers

What is you tanks actual water volume filled - 25 gals, assuming 2" of substrate and wood.

TDS before a WC - 305

How much water was changed - ~15 gal

What is the TDS of the mix (guessing 150ppm) - a simple average of what I added RO water and tap water) says ~137

But no clue what the change ratio is, (20%, 50% etc.) - 57%

And the resulting shift 30 minutes or more after - after 2 hours, TDS was 269.
 

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Looks like what 'I think' would be a normal shift result (imo) while you changed >50% the overall TDS difference between replacement and tanked, 305-137=168ppm this reduction further reduced by the ratio of change to remaining tanked. Substrates with a high CEC will aid in holding up high readings until the charged ions bonded to the sub reach equilibrium releasing into the softer water. Fert dosing, declor products, anything added to the water increases tested TDS. This topic is above my tanking pay grade for a precise answer.

I use 100% RO for water changes and don't ratio mix tap/product, I prefer to replace evaporation or water change with near zero TDS water. Hobby grade chemical tests won't register GH/KH as anything but zero and TDS is 1 or 2ppm. Tracking tank parameters using an excel spread sheet my results are in a different format for reference. I don't normally record post WC TDS but test GH/KH and then add minerals for set point recording that value in the log. The following day I test TDS for a 'clean' value then dose my first post WC fert addition.

43g water column - 34gWC = 85%WC
B4WC TDS 190ppm, 5dGH, 3dKH, NO3 5ppm, PO4 1ppm
after WC 1dGH, 1.5dKH, NO3 & PO4 0.0ppm / added 32 grams of GH booster which should increase my tank by 3dGH.
Post testing TDS 177ppm, 4dGH, 2dKH

Do have a couple tracks in similar format to yours. All added water was <2ppmTDS (basically distilled).
35g water column - 28gWC = 80%WC
B4WC TDS 225ppm / post 98ppm

43g water column - 30gWC = 70%WC
B4WC TDS 182ppm / post 89ppm

43g water column - 32gWC = 75%WC
B4WC TDS 212ppm / post 52ppm

63g water column - 31gWC = 49%WC
B4WC 289ppm post 152ppm

120g water column - 76gWC = 63%WC
B4WC TDS 254ppm post 93ppm

120g water column - 65gWC = 54%WC
B4WC TDS 223ppm post 94ppm

I don't know if anything offered here helps or not :redface:
 

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Discussion Starter · #5 ·
OK, I think I get it. My ECO complete is sustaining the higher readings and since I am adding ~150 ppm + ferts, that will keep the TDS up, so I need to let the system equalize over time and should check the actual conditions before ferts. I was adding tap water so that I don't shock my fish (just started trying RO water) and to help get up to match tank temp. Do you heat your RO somehow to match?

I am trying to match soft, low pH water for my Apistos. They are wild caught and while they have been doing "ok", I thought that they would like the softer water better. I guess I need a little help with the basics.

I thought that TDS helped define softness, but if ferts effect TDS, then that is not the only story. I know that GH and KH also represent hardness. What are the lower limits for these that would still be considered "soft" but won't allow a tank's pH to crash (i would like to be at about 5.5 - 6 pH with tds a about 100 ppm or so)? You indicated that you shoot for 3 GH. What about KH or do you not care. Do you add the minerals to the change water before placing in tank or add to tank after water change complete? I suppose my LFS has the minerals that I would need.

I find that the chem kits for hardness are a pain. I always end up with the mix on my hands as I take the top off and on. Have you found another tool to use?

I currently use excel and may not be getting the right carbon dosage into the tank. I plan to dabble with DIY CO2, but not until I get the water in better shape. I have plants that don't like the excel.

Thanks for your help.
 
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