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Discussion Starter · #1 ·
Newbie alert!

I have been mixing RO and TAP 50/50 without adding any minerals back. I figured my TAP KH, GH, and pH are too high so diluting it with RO will make it my target balance. I test the GH and KH in the mixture right away and it's my target 4 and 4. But maybe it isn't accurate because it needs an hour to change...?

The problem now is the KH in my aquarium is almost nonexistent (<17ppm) and GH is getting low (35-53ppm).

Are my plants eating up the minerals quickly and I need to add something to the aquarium? Or is my RO/TAP mixture lacking minerals?

I think my plants are deficient in calcium and magnesium because my cryptocoryne spiralis veins are dark green and outer leaf is lighter green. They are pretty tall for a 10 gallon tank and the roots are partially visible. I had trouble keeping them in the substrate. So it's possible they just don't like being in a short tank and the roots are not deep enough.

Would it be better to use 100% RO with Equilibrium and potassium bicarbonate? I already add KNO3 and KH2PO4 so they get enough potassium. Would it be better to use sodium bicarbonate instead?
 

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If you blend RO + Tap water in a bucket, and let it sit, does the GH and KH change over time (several hours or a day?)
Or does the extreme change only happen when the water has been in the tank for a while?

If it happens in the tank, then lets see if you can figure out why. Try this test:
Make the water blend you want, (perhaps a quart or two) then add a handful or two of substrate. Some substrates remove some minerals from the water. Stir and test over a few days (However long it takes the tank to change). If the sample does not show the same changes as are going on in the tank, then look for some other cause.
Other causes: Some aquarium additives can interact with the minerals in the water. Some things in the filter (water softener media) will remove minerals. Are there any of these in the system?

While you are trying to figure out what is what is going on, you might have to do something like this:
Make up the new water the way you want the tank to be. (GH, KH).
Do whatever amount of water change you want. Then monitor the tank through the week, and see if topping off with tap water is enough to add back the minerals, or add baking soda (sodium bicarbonate) for KH and Seachem Equilibrium for GH.
 

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Discussion Starter · #3 · (Edited)
If you blend RO + Tap water in a bucket, and let it sit, does the GH and KH change over time (several hours or a day?)
Or does the extreme change only happen when the water has been in the tank for a while?

If it happens in the tank, then lets see if you can figure out why. Try this test:
Make the water blend you want, (perhaps a quart or two) then add a handful or two of substrate. Some substrates remove some minerals from the water. Stir and test over a few days (However long it takes the tank to change). If the sample does not show the same changes as are going on in the tank, then look for some other cause.
Other causes: Some aquarium additives can interact with the minerals in the water. Some things in the filter (water softener media) will remove minerals. Are there any of these in the system?

While you are trying to figure out what is what is going on, you might have to do something like this:
Make up the new water the way you want the tank to be. (GH, KH).
Do whatever amount of water change you want. Then monitor the tank through the week, and see if topping off with tap water is enough to add back the minerals, or add baking soda (sodium bicarbonate) for KH and Seachem Equilibrium for GH.
The aquarium GH and KH drops a few days after wc.

When I blend the RO and TAP in a bucket I don't let it sit for more than 15 minutes before adding it to my aquarium. I put the RO in the bucket 1st then fill the rest with TAP so it is the right temperature. Add Prime for the TOTAL volume of bucket water. (Not just the TAP water amount. I hope this is correct.) I test the GH, KH, and pH of the bucket water 5-10 minutes later. GH and KH are both 4 drops (71ppm) and pH is 7.8 (which I'm ignoring).

The pH of my TAP water stays the same when it sits in a bucket for 24 so I didn't think it was necessary to age the water. I didn't test the GH and KH though.

If I understand correctly my substrate, UP Aqua Sand, is designed to pull minerals & ferts from the water. It has a high "cation exchange capacity." It's not really "sand."

I just bought Aragonite from a salt water aquarium store. I don't know the difference between that and crushed coral, but I was planning to add a little to a media bag for my filter to help buffer the KH. Now I'm second guessing if I should mess with that since it's calcium carbonate. Or at least hold off on adding additional variables while I figure out what's going on.

No I do not have any water softeners added to my filter. Just AquaClear sponge and biomax bag.

What is a safe amount of sodium bicarbonate to add to a 10 gallon without shocking ghost shrimp and a nerite snail?
 

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So it seems it is the substrate.

I would try the Aragonite. Yes, it is calcium carbonate, this is 2 of the things being removed by the substrate. Magnesium is the other mineral which we measure as GH, so if you find the Aragonite helps, you might also add a small amount of Epsom salt. Put the Aragonite into a mesh bag, or a nylon stocking and add it to the filter. Monitor the results, and you can remove the bag whenever you need to.

1 teaspoon of baking soda added to 30 gallons will raise the KH by 2 German degrees of hardness. This works like straight line math, so a 10 gallon tank would need 1/3 tsp to do the same. Start with 1/4 tsp, just in case the tank dose not actually have 10 gallons of water.
 

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Discussion Starter · #5 ·
So it seems it is the substrate.

I would try the Aragonite. Yes, it is calcium carbonate, this is 2 of the things being removed by the substrate. Magnesium is the other mineral which we measure as GH, so if you find the Aragonite helps, you might also add a small amount of Epsom salt. Put the Aragonite into a mesh bag, or a nylon stocking and add it to the filter. Monitor the results, and you can remove the bag whenever you need to.

1 teaspoon of baking soda added to 30 gallons will raise the KH by 2 German degrees of hardness. This works like straight line math, so a 10 gallon tank would need 1/3 tsp to do the same. Start with 1/4 tsp, just in case the tank dose not actually have 10 gallons of water.
24 hrs after adding 1 Tablespoon of aragonite (rinsed first) to a mesh bag in the filter:

KH went up from 0 drops to 2 drops (<17ppm to 35ppm)
GH went up from 2 drops to 3 drops (35ppm to 53ppm)

Perfect! Not too sudden. :) I just added 1/32 teaspoon of epsom salt after testing and will check it again tomorrow.

Thanks Diana! I really appreciate the mentoring!
 

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Discussion Starter · #6 ·
Would adding Excel be dangerous with a low KH? I have been holding off until I get my KH up and stable.

pH: 7.4 (pretty consistent)
KH: 0 d. (<17ppm) before wc, 2 d. (35ppm) after wc. It takes 48 hrs to drop down to <17ppm again.
GH: 3 d. (53ppm) before wc, 4 d. (71ppm) after wc. It takes 48 hrs to drop down to 53ppm again.
 

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Discussion Starter · #7 ·
Update - 3 weeks later KH is still dropping to <17ppm a few days after wc. The only way to keep it up is to add potassium bicarbonate every other day. The aragonite is still in the filter (1 Tablespoon). I'll try adding another Tablespoon.

Could low phosphates cause this? I haven't test the level. I'm still battling diatoms that live off high phosphates. That's one reason why I mix RO and TAP 50/50.

I started adding Excel 2 weeks ago to fight BBA and mostly for plant growth.
 

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I would make a regular program of adding GH booster and KH booster through the week. You could put more aragonite in the filter, see if that helps.
But you should be replacing the minerals as the substrate removes them. A little every 2-3 days. Do not add way too much on any one day. That would be too great a change in parameters.

Low phosphates would not cause GH or KH problems, but the plants need phosphorus. If the PO4 is under .5ppm then I would dose a little KH2PO4.
Diatoms need silica, which is present in a lot of materials.
 
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