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Captain
75g, 40g, 20g
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Discussion Starter #962 (Edited)
Subject: Failed experiment

Initial goal was to lower how much “stuff” I add to the RO water in an effort to supply the cleanest source water possible while still giving the plants what they need to grow. (started the decline sometime in December 2020).

I ended up “thinking” I was dosing my RO drum to 16ppm CaSO4 and 5ppm MgSO4 each time I did a water change. The method I was using to get to the 16 / 5 amount was to test the ppm TDS of the RO drum water after a fill up, then add enough CaSO4, MgSO4 and K2CO3 to get back to my target ppm TDS and 1dKH. (target ppm TDS value was based on dGH information supplied by Rotalabutterfly for Ca & Mg, then calculated out to an approximate ppm TDS which also included the ppm TDS of the actual RO water with nothing added).

Now, anybody out there figure out where I might have gone wrong yet?

It would seem 1dKH of K2CO3 actually adds a fair amount of ppm TDS to the equation. I was not accounting for that and basically the end result was my aquarium water column Ca & Mg levels decreased a specific amount with each water change. Kinda a reverse accumulation if you will.

I could not find any reliable info on how much ppm TDS 1dKH would add to a given volume of water so I ended up doing my own non-scientific experiment. Started with 1 gallon of TAP water and measured the ppm TDS of that. Then calculated how much K2CO3 would be needed to raise the KH of the gallon of water by 1dKH. Added that amount and gave it some time to dissolve (about an hour). Would seem that tiny amount of K2CO3 raised the RO water level 18.5ppm TDS.

My best guess is my aquarium water column was down to around 9 to 10ppm Ca. This, it seems, lead to many unhappy plants. Which lead to some poor growth. Which I believe gave the green dust algae a prime opportunity to say hello and stick around for awhile. For now, my water column will be correctly dosed to 20ppm Ca and a total of 7.35ppm Mg (additional Mg from MgNO3). Fingers crossed I will get back to happy plants again.

And if anyone is interested, water change volume is 75% per week and the latest “dosed” N/P/K is 12/6/18
 

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Captain
75g, 40g, 20g
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3,794 Posts
Discussion Starter #963
Have been wanting to do this for awhile - just never seemed to have time.
1027670

Another interesting development (experiment?) since my last post - I added diffusers to my Radion XR-15 freshwater lights.

Was dealing with a lot of GDA. Finally pulled out the Seneye to check things out... well, about 4" above the substrate was 150ish PAR and right under the light, 1" below the surface it was 540ish PAR. WOW, maybe OK for @Greggz 's tank, but not good for my tank. So, I turned down the lights to about 105 PAR at the substrate which is more reasonable, but I was still getting a pretty hot spot right under each light. So, DIY to the rescue (factory diffusers are like hens teeth these days). I used a clear prismatic polycarbonite diffuser. The hot spot is much more diffused and the substrate PAR dropped to 90-94. Will run with this setup for a month or so and see how the plants like it.
 

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Have been wanting to do this for awhile - just never seemed to have time.
View attachment 1027670
Another interesting development (experiment?) since my last post - I added diffusers to my Radion XR-15 freshwater lights.

Was dealing with a lot of GDA. Finally pulled out the Seneye to check things out... well, about 4" above the substrate was 150ish PAR and right under the light, 1" below the surface it was 540ish PAR. WOW, maybe OK for @Greggz 's tank, but not good for my tank. So, I turned down the lights to about 105 PAR at the substrate which is more reasonable, but I was still getting a pretty hot spot right under each light. So, DIY to the rescue (factory diffusers are like hens teeth these days). I used a clear prismatic polycarbonite diffuser. The hot spot is much more diffused and the substrate PAR dropped to 90-94. Will run with this setup for a month or so and see how the plants like it.
Thanks for supplying the plant identification picture. It's something that people like me, who are new to the planted world, really appreciate!

Your tank is looking very nice!
 

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Captain
75g, 40g, 20g
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Discussion Starter #965
Thanks for supplying the plant identification picture. It's something that people like me, who are new to the planted world, really appreciate!

Your tank is looking very nice!
Thank-you. I seem to remember saying pretty much the same thing when I first started - really nice to know what all the plants are called. And to be perfectly honest, all those plants have come from 4 of 5 members on this forum (along with probably 20 others that I could not keep alive)
 

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Thank-you. I seem to remember saying pretty much the same thing when I first started - really nice to know what all the plants are called. And to be perfectly honest, all those plants have come from 4 of 5 members on this forum (along with probably 20 others that I could not keep alive)
I was unaware that you were keeping members of the forum alive. Remind me to never allow you to keep me alive!

I could go through your journal to discover what substrate you're using or could simply ask you. After the comment above I guess I'll have to ask very nicely. Therefore, can you pretty please let me and all the other members who are still alive what substrate you're using?
 

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Captain
75g, 40g, 20g
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3,794 Posts
Discussion Starter #968
Very cool! I have Radions, too, and look forward to your thoughts on how the diffusers work out

Meantime, your tank is looking great and I really appreciate the plant listing/lineup
Interesting, was not sure anybody else was running these lights.
Here is the start of the experiment. Because of the line of sight from the couch to the lights, I added these corrugated white plastic shields. I was intrigued at how the shields better reflected what the actual color of the light was vs what my eyes could see in the tank. In this picture, I pretty much made a crude frame to hold a piece of acrylic prism that I bought at Lowes.
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I added this single diffuser to the right hand light on my 75g tank. Notice how the color on the corrugated white plastic shield looks different. This picture was actually taken 5 days after the diffuser was installed. Look at the back glass wall of the tank. Notice which side has the GDA and which side doesn't.
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I eventually added diffusers to all 3 lights. The end result is pretty amazing. Much less GDA. Now, the real question is - less algae because of less overall light? less algae because the hot spots are diffused?
My guess is less overall intensity of light.
Here is what the diffuser looks like on the light. Not pretty, but for now it works. I eventually will have my friend with a 3D printer make something nice looking.
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1027701
 

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Captain
75g, 40g, 20g
Joined
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3,794 Posts
Discussion Starter #969
I was unaware that you were keeping members of the forum alive. Remind me to never allow you to keep me alive!

I could go through your journal to discover what substrate you're using or could simply ask you. After the comment above I guess I'll have to ask very nicely. Therefore, can you pretty please let me and all the other members who are still alive what substrate you're using?
LOL - made me smile.
5+ year old Eco Complete is what I am using. For all the complaints about being hard to plant in, I guess I have gotten used to it. I am also finding that I need to do more deep vacuuming of the substrate (getting pretty dirty down there).
Could the plants do better with something else - probably.
I guess in the interest of the forum members that are still alive - I would assume they would send me something better so that I would not have to work so hard at keeping them alive ;-)
 

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I really like your clear diffuser idea!! Since I did the DIY on my LED lights, I've never really liked the thought of 4 hot spots across my tank, if I get time, I may have to do the same this weekend!

Sent from my Pixel 4 XL using Tapatalk
 

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I ended up “thinking” I was dosing my RO drum to 16ppm CaSO4 and 5ppm MgSO4 each time I did a water change. The method I was using to get to the 16 / 5 amount was to test the ppm TDS of the RO drum water after a fill up, then add enough CaSO4, MgSO4 and K2CO3 to get back to my target ppm TDS and 1dKH. (target ppm TDS value was based on dGH information supplied by Rotalabutterfly for Ca & Mg, then calculated out to an approximate ppm TDS which also included the ppm TDS of the actual RO water with nothing added).
You're way past this now, but I'm curious. Did you take into account the effect of the SO4 on TDS? I'm no chemist, but by my calcs, adding CaSO4 to give 16ppm Ca will also add 38ppm SO4, giving a total of 54ppm TDS total. The reading I've done suggests that sulfates contribute to our TDS amounts. Last time I remineralised my RO water, I tested TDS before and after the addition of CaSO4 and MgSO4 and the TDS readings seemed to include the SO4. I'm using a calibrated Apera TDS pen so trust the readings I'm getting.

By the time I add 23ppm Ca, 8ppm Mg, 20ppm NO3, 4ppm PO4 and 40ppm K, my RO drum has gone from 4ppm to 185ppm.
 
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