[Raymond S.]

If fish waste will re-mineralize it then it will mineralize plain gravel also.
The reality of that one is that it will...in limited quantities.
For anything like a full house of plants you will eventuially need to add ferts as the
soil will run out of it's own nutrients much the same as a potted plant though not as fast.
Go to any on-line pet supply and use any substrate listed(except Laterite) or use
Pool Filter Sand or blasting sand but don't get a substrate that is for salt water tanks.
That can be confusing but anything that has the word coral in it is salt water and
just ask here about any other you are not sure about.
You can also get this same info by reading some in the section where you put this question. Just look down the list for ones which name a specific type. This is especially true if any say "List your favorite substrate."
I have plain gravel with Flourie on top of it in one of my tanks and Eco-Complete in the other one.

 

[jrman83]

Fish waste provides nutrients for plants but it does not have everything the plants need or people with heavily stocked tanks wouldn't need to dose their tanks with ferts. Any nutrient rich substrate, like MTS maybe, will eventually not have the same level it started with. When it reaches the point that it runs out could be somewhat subjective but it will reach a point when the richness of the soil has less of an impact.

 

[Mxx]

Depends...

There are relationships between speed and intensity of plant growth, how much food you put in, your lighting intensity, whether you are using CO2 or not, your fish stocking density, whether you are cleaning your tank or not, what amount of plant matter you might be removing through pruning, and how much food you are putting in for your fish.

Basically, that may or may not be a balanced relationship as to whether nutrient input via fishfood is more or less than what your plants require. If it's less, than an enriched substrate such as MTS will get depleted over time.

According to Ecology of the Planted Tank, the proportions of nutrients in fishfood are pretty much in the proportions which your plants happen to require as well.

 

[Monster Fish]

It will eventually run out but it should last you longer than a year depending on how fast you drive the plants to grow and how weedy they are. If the MGOCPM you use was unsifted and retained the bark and other larger pieces, they will break down, mineralize, and become plant food. Fish waste and decaying food and plant matter will eventually break down into mulm which will help enrich your dirt layer but this might take a while. Check out wkndracer's dirted tank journals. He has a few MGOCPM tanks that have pushed past the 18 month mark without any additional dosing or ferts.

 

[Diana]

Fish food tends to be lowest in K, Ca, and Fe.
Some soils have a good supply of fertilizers, or you can add ferts, so they last a long time. If you put some slow release fertilizers deep in the soil it will take a long time for them to be depleted.

Water can supply the Ca, as long as the GH is over about 3 degrees.

As noted above, the faster you want the plants to grow (high light, added CO2) the more fertilizers the plants will demand.
Even in a low tech set up with high fish loads (slow growing plants with lots of fish food) my plants were showing potassium deficiencies. So I started by adding a combined product with K and Fe.
As I improved other conditions (more light, Excel and yeast/sugar CO2) I had to add more ferts.

Think of soil as if it is your dinner plate, and you can easily see that you have to keep buying more food to put on the plate.

 

[kidgrave]

Fish food tends to be lowest in K, Ca, and Fe.
Some soils have a good supply of fertilizers, or you can add ferts, so they last a long time. If you put some slow release fertilizers deep in the soil it will take a long time for them to be depleted.

Water can supply the Ca, as long as the GH is over about 3 degrees.

As noted above, the faster you want the plants to grow (high light, added CO2) the more fertilizers the plants will demand.
Even in a low tech set up with high fish loads (slow growing plants with lots of fish food) my plants were showing potassium deficiencies. So I started by adding a combined product with K and Fe.
As I improved other conditions (more light, Excel and yeast/sugar CO2) I had to add more ferts.

Think of soil as if it is your dinner plate, and you can easily see that you have to keep buying more food to put on the plate.

Are you Diana Walstad? Thanks for your reply. What type of ferts do you use for K and Fe? I bought some dry ferts so I think I'm going to use those in case I see potassium and Fe lacking. Do you ever use clay for iron?

 

[kidgrave]

It will eventually run out but it should last you longer than a year depending on how fast you drive the plants to grow and how weedy they are. If the MGOCPM you use was unsifted and retained the bark and other larger pieces, they will break down, mineralize, and become plant food. Fish waste and decaying food and plant matter will eventually break down into mulm which will help enrich your dirt layer but this might take a while. Check out wkndracer's dirted tank journals. He has a few MGOCPM tanks that have pushed past the 18 month mark without any additional dosing or ferts.

I have a low-tech tank. I have a 10 gallon with 2x13 watt CFLs. I have a question. With dirted tanks, is it ever necessary to do a gravel vac?

 

[Monster Fish]

I have a low-tech tank. I have a 10 gallon with 2x13 watt CFLs. I have a question. With dirted tanks, is it ever necessary to do a gravel vac?

Never do a deep gravel vac. Just a surface vacuum every once in a while to remove any excessive mulm if it bothers you or any escaped dirt after a rescape.

 

[Diana]

I am not Diana Walstad.

I started using Leaf Zone for K and Fe.
As conditions in the tanks improved I moved to the EI method, including dry ferts.