Old Tank Syndrome?

[Hobbit]

From what I understand, old tank syndrome is when your plants have used up the nutrients in your substrate that fish mule doesn’t effectively replace. Is this right or is there more to it? And is the remedy as simple as root tabs and fertilizer?

My 55 gallon has been running for a year and stem plants just don’t do well in it anymore. (If I buy more of them I’ll be buying some root tabs for sure!) 

Should I be afraid of OTS, or is it nothing to fear?

@Streetwise since you run a lot of Walstad tanks I’d love to hear your thoughts on this.

[Koi]

I think what you said could be true but usually when I think of old tank syndrome, i'm thinking of nutrient build up for other things we are not testing for. A good way to try to prevent I find is to do 50% or more water changes every now and then to  reset your tank parameters. If you haven't seen this video, it might help you conceptualize that idea.

 

[Streetwise]

In Diana Walstad's book, The Ecology of the Planted Aquarium, Section VIII, G, 5, she says,

Quote

“Gravel substrates—unless they have undergravel filters-- will degrade with time. As they collect organic matter and become increasingly anaerobic, they will release toxins that will endanger the fish. However, aquariums with soil substrates and rooted plants seem to do well indefinitely without any maintenance (e.g., gravel vacuuming).
Ironically, some soils that start out bad can improve with time. I had algae problems for several months in one tank that I set up with an over-fertilized potting soil. Five years later, it’s the tank with the best plant growth.”

Excerpt From: Diana Louise Walstad. “Ecology of the Planted Aquarium.” Apple Books. https://books.apple.com/us/book/ecology-of-the-planted-aquarium/id661029773

Later, she adds:

Quote

“Nutrient depletion should not cause the substrate to give out. If you allow mulm to accumulate and replenish the nutrients removed by the plants, the soil should continue to support good plant growth for many years. I have three tanks that have the same potting soil underlayers they started with 6 or 8 years ago, and the plants continue to do very well. Other tanks with garden soil underlayers have been doing well for the last 4 to 5 years.”

Excerpt From: Diana Louise Walstad. “Ecology of the Planted Aquarium.” Apple Books. https://books.apple.com/us/book/ecology-of-the-planted-aquarium/id661029773

I don't have any tanks that old yet, but I never gravel vacuum, and I rarely change water.

[Hobbit]

Thanks @Koi! I should have assumed Cory had a video on this before I asked. 😄 More recently Cory’s advocated for a less frequent water change schedule, so I wonder if his thinking has evolved on this a bit. I’d imagine it depends somewhat on what’s in your tap water.

8 minutes ago, Streetwise said:

Gravel substrates—unless they have undergravel filters-- will degrade with time. As they collect organic matter and become increasingly anaerobic, they will release toxins that will endanger the fish. However, aquariums with soil substrates and rooted plants seem to do well indefinitely without any maintenance (e.g., gravel vacuuming).

Sooo I have soil capped with gravel in my tank... What does this mean for me? 😜 I do have lots of MTS in there as well as two loaches, so hopefully things get stirred up enough to prevent large anaerobic pockets.

Honestly I may just not have had enough soil in there to start with. I did get much better plant growth in the first few months than I do now.

My issue with soil depletion may also be due to my tank being understocked. I don’t want to cram it but I will be adding some more fish soon.

Do you add any ferts to your tanks at all @Streetwise? Potassium or anything? And are you able to grow stem plants?

[Streetwise]

I have experimented with Easy Green, but I think it just helped the algae, since my tanks have so many nutrients already. I tried root tabs once, but my Yoyo Loach dug them all up.

My soil is also capped with a bit of sand and a bit of gravel, with slightly different layerings depending on when I set them up. I created some issues early on, when I was going too deep with soil, and/or too deep with cap, and making anaerobic conditions for the roots, which was particularly noticeable with Amazon Swords. I had to remove a lot of material to get things back in balance. I think adding more plants also helped.

I would suggest that you let the mulm accumulate and get absorbed back into the substrate. If you want to check for anaerobic conditions, you can probe your soil with a skewer or chopstick. I have done that with new tanks to release gas a few times until the plant roots got established. I am also very picky about hardscape, so I try to avoid using big rocks that would cover a big section of substrate, and I try to use my wood so that it is not sitting with a flat section down, but instead like a tripod, where only points are touching.

I can grow stem plants, but I don't have more than one or two anymore, because I would run out of space to trim and replant.

Cheers

[Koi]

21 minutes ago, Hobbit said:

Thanks @Koi! I should have assumed Cory had a video on this before I asked. 😄 More recently Cory’s advocated for a less frequent water change schedule, so I wonder if his thinking has evolved on this a bit. I’d imagine it depends somewhat on what’s in your tap water.

Sooo I have soil capped with gravel in my tank... What does this mean for me? 😜 I do have lots of MTS in there as well as two loaches, so hopefully things get stirred up enough to prevent large anaerobic pockets.

Honestly I may just not have had enough soil in there to start with. I did get much better plant growth in the first few months than I do now.

My issue with soil depletion may also be due to my tank being understocked. I don’t want to cram it but I will be adding some more fish soon.

Do you add any ferts to your tanks at all @Streetwise? Potassium or anything? And are you able to grow stem plants?

Definitely everyone's tap water plays a role in how we go about maintaining our tank. A buildup issue that I have to keep an eye is Nitrogen. Nitrite and nitrate are both present in my water and I would say I stock my tank a little more heavily than what is generally considered ok. That being said even with a 50% water change, my tank is producing/getting more nitrates than I take out just because of my tap. To circumvent this nitrate buildup I've lightened up my feeding and instead of changing water once a week its around once every 4-5 days so that my nitrates stay around 20-40.

And yes I think there are a lot of advantages to keeping stable water parameters as apposed to changing water just because you always do it at the end of the week. I think most people would prefer to be able to change less water but you kinda have to weigh the pros and cons of how much water you're changing. For an extreme example say your nitrates are at 100 ppm, most people would agree that 100 ppm nitrate is probably more harmful than change of water parameters by adding fresh water. Other than that I definitely agree changing water too much isn't a good thing.