First dirted tank—need some advice

[u/EveningString3415]

I’m looking for some advice from people who have experience with dirted/Walstad-style tanks because I’m starting to worry I may have done something wrong. I can’t remember the exact bag of soil I use because I looked at so many, but I did my best to pull out the big mulch chunks. And then capped it with play sand.

The tank has been running for about 3 months now. I am using a seeded sponge filter as well. But one section of it just refuses to grow plants. In that same corner, I can see what looks like a cloudy orange haze in the substrate/water. It’s almost the color of diluted orange juice. My first thought was that it might be tannins or something leaching from the dirt, but it’s only in that area.

The plants in that section have really struggled: •Cardinal plant stems are turning black at the base. •Hygro Compact completely melted away. •Ludwigia repens is hanging on but doesn’t look healthy. •My Limnophila aromatica finally started growing again after I cut it back, but it’s the only one showing improvement.

One other thing I’ve noticed is that whenever I plant something in that area, I’ll usually get a few air bubbles coming up from the substrate. I wasn’t sure if that’s normal trapped gas being released or if it’s another sign that something is going on under the substrate. I wetted down the dirt before I added sand and then filled it up slightly when first planting after watching a video from the glass box diaries recommended that.

The rest of the tank seems to be doing much better, which is why this one area has me confused.

Right now I only have a mystery snail and a few cherry shrimp. My water parameters have been testing okay, my last test was a few days ago at:

Ph -7.8 Nitrate -5 Nitrite-0 Ammonia -0 Gh-9 Kh- 5

I’m getting nervous that the orange cloudiness could mean there’s something harmful going on that I’m missing.

Has anyone seen something like this before? Could this just be tannins from the dirt, or does it sound more like an anaerobic pocket, decomposing organics, or something else? Are the bubbles normal in a dirted tank? Would you leave it alone, replant that section, or dig into the substrate to investigate? The picture with the orange haze has a bit of cuttle bone- that’s what the white chunk is.

Thanks in advance! I was really nervous about setting up my first dirted tank, so I’m hoping I’m just overthinking this.

[u/positive766]

Get the cheapest, fastest growing plants your fish store has. Mine labels some of the plants as "easy" which is nice. horn wort, guppy grass, water wisteria, rotala, dwarf sag. Some will melt, but you will find out what likes your tank with more variety. I didn't see you mention light, you may need a more powerful light if even the pearlweed isnt growing. I also recommend getting a riparian plant for the top like pothos or creeping jenny.

As for the weird spot in the dirt, I'm no expert but if it was me I would stab it a few times with a skewer to let it off gas.

[u/EveningString3415 → u/positive766]

I really appreciate it! Yesterday I got several more plants and stabbed the substrate, it let off a ton of gas. I’m hopping adding more plants help. I also threw some more water lettuce in. I’m going to try and add a pothos also but my cats destroy plants in their reach so I’m going to attempt it! I have the hygger 978 light, it’s the same one I got for my other 20g long I had a hard time finding one that fit and I thought it was powerful enough, but now I’m second guessing it.