KH very low - how do I increase it?

[Django]

I found one thread on this subject but there really weren't enough details about what two chemicals to use to raise KH and how much to use. I want to get to 2 dKH.

My KH is <= 1 dKH. pH is 7.0 - 7.2. NO3 is 20 ppm. I don't know how KH has gone down, but ph used to be 7.6 closer to when I started the tank. It's a 10 gallon tank, moderately planted, lightly stocked.

Can you help me do this?

[mltreat]

Why do you want to increase the KH? I thought a higher KH was associated with harder water. Well, I bet you could use baking soda to increase the CO2 content, which will increase the KH. You could also just use CO2 injection. We use yeast in a 2L bottle. Look for a "do it yourself" yeast project. Remember your pH will go up if you use baking soda or CO2.

[Diana]

KH is carbonate.
To raise the carbonate level in the water, add carbonate.
If your tap water has at least 2 degrees of KH, then do a lot more water changes. This is adding carbonate with every water change. If your tap water is also very low in KH, then you will have to add carbonate some other way. (Keep up the water changes, though, they are good for other reasons)
Baking soda is the most common and cheapest way to do this. 1 teaspoon of baking soda added to 30 gallons will raise the KH 2 German degrees of hardness, and will raise the pH a bit. In a 10 gallon tank I would try 1/4 tsp and test. If that is OK, then simply monitor it and add a bit whenever you need. If 1/4 tsp is not quite right try adding another 1/8 tsp. Do not add more than that at one time. Let the fish acclimate to the slightly harder water, then alter it again in a few days, if needed.
Other materials that have carbonate:
Calcium carbonate
Potassium bicarbonate.

Is the GH in your tank OK? Calcium carbonate will raise the GH, too.

What substrate do you have in your tank? Some of the substrates with high cationic exchange capacity will remove the carbonates.

Nitrifying bacteria use the carbonates as a source of carbon. If they are low to start with the bacteria can remove them.

Some plants use carbonates as a source of carbon.

What is the KH in the tap water?
------------------------------------------------------------
Has the tank been running a long time? There is a problem that can develop called Old Tank Syndrome. The solution is to do lots of small water changes until the tank is back on its feet again.

[Diana]

Another way to do this is to add coral sand, limestone or oyster shell grit to the filter. I use a nylon stocking to do this.
These materials have other minerals as well as carbonate, and will raise the GH, too.

[Django]

Originally Posted by Diana

KH is carbonate.
To raise the carbonate level in the water, add carbonate.
If your tap water has at least 2 degrees of KH, then do a lot more water changes. This is adding carbonate with every water change. If your tap water is also very low in KH, then you will have to add carbonate some other way. (Keep up the water changes, though, they are good for other reasons)
Baking soda is the most common and cheapest way to do this. 1 teaspoon of baking soda added to 30 gallons will raise the KH 2 German degrees of hardness, and will raise the pH a bit. In a 10 gallon tank I would try 1/4 tsp and test. If that is OK, then simply monitor it and add a bit whenever you need. If 1/4 tsp is not quite right try adding another 1/8 tsp. Do not add more than that at one time. Let the fish acclimate to the slightly harder water, then alter it again in a few days, if needed.
Other materials that have carbonate:
Calcium carbonate
Potassium bicarbonate.

Is the GH in your tank OK? Calcium carbonate will raise the GH, too.

What substrate do you have in your tank? Some of the substrates with high cationic exchange capacity will remove the carbonates.

Nitrifying bacteria use the carbonates as a source of carbon. If they are low to start with the bacteria can remove them.

Some plants use carbonates as a source of carbon.

What is the KH in the tap water?
------------------------------------------------------------
Has the tank been running a long time? There is a problem that can develop called Old Tank Syndrome. The solution is to do lots of small water changes until the tank is back on its feet again.

Thank you.

GH is 5dGH. I have to add Equilibrium every water change. Tapwater KH is 2dKH, so that's what I'd be shooting for. I do 25% water change once a week. I would like to bring the tank back to 2dkh and just go from there.

I have natural gravel (too big) as my substrate. Getting interested in soil capped with sand.

The 20 ppm nitrate measurement I think indicates increased nitrifying bacteria activity. It was zero for a long time. During that time the plants were showing fast growth. Lately I've been having growth problems with the plants. I started the tank the middle of April.

Thanks very much for helping me.

[exv152]

Originally Posted by Django

Thank you.
GH is 5dGH. I have to add Equilibrium every water change. Tapwater KH is 2dKH, so that's what I'd be shooting for. I do 25% water change once a week. I would like to bring the tank back to 2dkh and just go from there.

I have natural gravel (too big) as my substrate. Getting interested in soil capped with sand.

The 20 ppm nitrate measurement I think indicates increased nitrifying bacteria activity. It was zero for a long time. During that time the plants were showing fast growth. Lately I've been having growth problems with the plants. I started the tank the middle of April.

Thanks very much for helping me.

The most effective way to increase KH is to add some alkaline buffer (seachem) but you only need to keep the KH somewhere around 1º or slightly more, this will prevent pH crashes, but anything higher will increase the pH and hardness above 7. As for your plant growth decreasing, this is normal especially if you're not adding anything like liquid ferts or tabs. The plants may have used up all the initial micro nutrients in the tank. I would suggest adding more seachem equilibrium than you're adding already, once a week.

[Seattle_Aquarist]

Hi Django,

I have the same problem here in the Seattle area; my water comes out of the tap at <1.0 dKh. In order to avoid the possibility of having my PH 'crash' I like to keep my dKH at about 2.0 so I Bicarbonate of Soda (Arm and Hammer Baking Soda). Here is the calculator I use to determine how much baking soda (not baking powder) I need to add.

[Django]

Thanks both of you. Helped a lot.

[Diana]

Equilibrium is not a complete fertilizer. It has potassium, which is a fertilizer, but I would not add more, since you are already keeping the GH at 5 degrees.
Nitrate seems OK at 20 ppm, or you could increase the water changes a bit and get the nitrite down a bit closer to 10 ppm.
If the nitrate is from fish food, then it is likely that phosphate is about right, too, and probably most trace minerals. Maybe not iron, though.
When I started growing aquatic plants the first nutrients they needed were Iron and Potassium. You are adding the potassium, so I would look into an iron supplement.
The next this is increasing the carbon in the tank. Excel is good for that, but not all plants accept Excel.

[Django]

Originally Posted by Diana

Equilibrium is not a complete fertilizer. It has potassium, which is a fertilizer, but I would not add more, since you are already keeping the GH at 5 degrees.
Nitrate seems OK at 20 ppm, or you could increase the water changes a bit and get the nitrite down a bit closer to 10 ppm.
If the nitrate is from fish food, then it is likely that phosphate is about right, too, and probably most trace minerals. Maybe not iron, though.
When I started growing aquatic plants the first nutrients they needed were Iron and Potassium. You are adding the potassium, so I would look into an iron supplement.
The next this is increasing the carbon in the tank. Excel is good for that, but not all plants accept Excel.

Thank you for the help.

I just add Equilibrium with water changes. Tap water GH is something less than 5 dGH, and it was suggested that I add Equilibrium to avoid deficiency. I started dosing Flourish Complete recently at four times what I was dosing it before, still a small amount. I guess I was a little low.

Fish food is a likely enough the source of some of the nitrates, I hope none is from the Flourish Compl. Nitrates were unmeasureable for a couple of months when the plants were flourishing. Good news is they're growing well again and I'm expecting nitrates to go down. I have a HOB on my 10 gal. but generally not much agitation, so I'm hoping that a lot of the CO2 that is generated stays in the water through some part of the day.

I just bought some Arm & Hammer, so hopefully KH will be back to 2 dKH soon.

[xenxes]

Why do you need to increase KH btw?

[Diana]

Carbonates are a source of carbon for nitrifying bacteria.
Carbonates are a source of carbon for some plants.
Carbonates are a buffer that stabilizes the pH.

I have run tanks where the substrate sequestered all the carbonates, the KH showed 0 on 2 tests, and the pH showed 6.0 (lowest the tests went). Tank was fine, even when I did water changes with tap water (KH about 4-5 degrees, pH in the upper 7s).
I was adding Excel for carbon, then, so the plants that might have switched to carbonate sources did not need to. No nitrogen cycle issues, either. Perhaps the bacteria lived in the substrate, close to the carbonates the substrate had removed from the water. I do not know if the bacteria could use those carbonates.

[Django]

I read a short section on carbon http://www.etap.org/demo/biology_fil...ion4tutor.html
and I think I understand some of the importance of carbon. By not supplying the full complement of CO2 I'm limiting the growth of my plants. I'm new to plants, though - started my tank in April. What I have learned has been through word of keyboard. You can magine some of the things I've heard. It would require a leap of faith for me to try some different things.
Anyway, thank you very much. I would really appreciate it if you could throw a coouple of links about carbonates and plants this way.

[Diana]

Best info about plants is Diana Walstad's book: Ecology of the Planted Aquarium.
All sorts of information, most of it backed up with research and all of it backed up with tons of references.

All other info is in bits and pieces, and can be sort of hard to put it all together.

[exv152]

If your alkalinity is going down it's because the plants are depleting the KH, HCO3 and bicarbonates as alternate sources of carbon. All plants prefer co2, but if that's not available, some will use just about any carbon while other more demanding plants will just wither. If your KH is going down that's a good sign you need to add more co2, or reduce your lighting.