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Discussion Starter · #1 · (Edited)
About two months ago I started my first Walstad style tank. I used 1 inch of miracle gro and added 1 inch of black sand on top, and I've added a variety of plants such as rotala rotundifolia, cryptocoryne wendtii, bacopa caroliniana, and pearlweed, as well as salvinia minima at the surface. Everything has been going pretty smoothly. The tank stabilized a bit about two weeks ago, and I've had good growth with everything and added some snails. I'd like to add some amano shrimp I have from another tank, but I'm hesitant to do so.

My water from the tap has a pH of 7. The other tank with the shrimp has a pH of 7.6, probably due to the crushed coral that has been sitting in the filter. The planted tank I've been working on, however, has a pH of 6.0, if not lower. I feel like such a change would probably hurt my shrimp, so I've been very hesitant to move them.

I've added some crushed coral to this tank, too, and yet the pH has stayed the same. It only ever rises to 6.4 if I perform a 20 - 30% water change, but the day after it falls back down to 6 (that's the minimum on the API test kit). There are a few things I can think of: 1) this tank doesn't have a filter, and the crushed coral sits on the substrate. With that being the case, I assume that it doesn't dissolve and release minerals as quickly as crushed coral that's in circulating water in the filter, therefore not buffering the water. 2) The lack of circulation is inhibiting gas exchange, allowing for co2 to be expelled from the water at a much slower rate than if there ample water agitation, causing the pH to remain low.

I was looking to not add a filter because I wanted to go the Walstad route completely and also not deal with more frequent evaporation from the filter. Is implementing a filter the only solution, or is there something else I can do?
 

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Welcome to the planted tank!

You may be right in that the lack of circulation accumulates CO2, although I am not sure where that would be coming from.
I would suggest that the Miracle Gro might be leaching humid acids which bring down the pH.
The best way to fix that IMO would be large, frequent water changes for a few weeks.

I don't remember all about the Walstadt method, does it discourage water changes?
I have found both water changes, and some good circulation (not strong, and doesn't need to be a filter, there are internal pumps available too) go a long way in maintaining a tank healthy.
 

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Discussion Starter · #3 ·
Welcome to the planted tank!

You may be right in that the lack of circulation accumulates CO2, although I am not sure where that would be coming from.
I would suggest that the Miracle Gro might be leaching humid acids which bring down the pH.
The best way to fix that IMO would be large, frequent water changes for a few weeks.

I don't remember all about the Walstadt method, does it discourage water changes?
I have found both water changes, and some good circulation (not strong, and doesn't need to be a filter, there are internal pumps available too) go a long way in maintaining a tank healthy.
Thanks!

I actually tried something a little different. I did a partial water change in which I actually added in some water from my other tank that has a pH of 7.6. This brought up the tank's pH to 6.6, and it has stayed there for at least a week now. I guess the water contained enough calcium carbonate to buffer the tank and deal with the tank's acidic conditions, which I'm really glad to see.

I think the idea is to pretty much let the tank run its course without doing much in terms of water changes, as the plants are supposed to act as the biological filter and uptake ammonia and other nutrients from the water and substrate.

The only issue that remains now is that the tank is a bit cloudy, but I'm sure a few water changes will fix that up.
 

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Discussion Starter · #4 ·
Thanks!

I actually did a water change with water from my other tank that has a higher kh, and that seemed to do the trick. The tank's at a stable 6.6 now, which is a huge relief. I acclimated all my shrimp two days ago and they're doing really well.

I think the idea is to let the tank run its course and not really do water changes after a period of time, as that leads to taking out nutrients that plants would be using up otherwise.
 

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I've never been a big fan of these "no water change" approaches. I think our systems are too small to be truly balanced. In theory it should work, but I fear Liebig's law of minimum bites us in the end. :nerd:

But... kudos if you can make it work!
 
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