I was thinking about using this brand for a fishless tank with species of plants that take up nutrients from the water column (anubias, java fern, banana plant).

Schultz 10-15-10 Plant Food plus Micronutrients:

Total Nitrogen 10%
1.6% ammoniacal nitrogen
0.2% nitrate nitrogen
8.2& urea nitrogen

Available Phosphate 15%

Soluble Potash 10%

Iron (chelated) 0.1%

Manganese 0.05%

Zinc 0.05%


I've read that these fertilizers aren't recommended for aquariums, though I've only read about them possibly being harmful to fish. Are they also harmful to aquatic plants? The only animals that I plan on keeping in this setup are ramshorn/pond snails to control algae growth.

I believe that it's the urea buildup that is the issue in a closed system (aka aquarium). Also want to avoid heavy metals, like zinc.

I'm not sure if they would be harmful per se, but the nutrients required for terrestrial garden/house plants (for which these products were designed) are inherently different than those needed by aquatic species or terrestrials in an aquatic stage. Therefore you will likely run into issues. The doses of nutrients required for terrestrial plants are generally greater, largely because they are not in an enclosed system- many of the nutrients are lost through the soil and by water washing them away. They'll also be able to absorb more from superior access to CO2. With a fish tank, it's a closed system- everything you put into it stays there, until you remove it (taking out plant cuttings, water changes etc). Aquatic plant fertilizers are specialized to provide only what the plants can use up, and I feel that a terrestrial grade fertilizer would offer a surplus of nutrients. These nutrients behave differently from each other, so would remain in the water, get absorbed by the plants, be lost into the atmosphere or be converted into other forms of the element at different rates, making it difficult, if not impossible to simply does the tank and leave it. If you were to use this, I would recommend doing a large water change each time you dose, and several in between dosing.

Just to be clear, none of this is factually or scientifically based, it's just my non-backed assumptions, so should be viewed as pseudoscience until proven otherwise... and now that I think about it, I knew of a guy who had a fantastic paludarium setup with healthy underwater plants who dosed miracle gro fertilizer. So go ahead, experiment, see where it gets you! You'll never know for sure until you try it.

Thanks for the replies. I forgot to mention that I will also be growing pothos and syngoniums in that same tank (with the leaves above water). So those should help to keep any excess nutrients down if I try the houseplant ferts.

I do have a couple of small bottles of flourish comprehensive, but that is formulated with the idea that the nitrogen and phosphate would be supplied by the fish waste. I might try dosing with a combination of the schultz and the flourish comprehensive and just keep an eye on the plants. I plan on getting an EI dry fertilizer package at some point. But since I have those other ferts already, I figure that it's worth experimenting in small quantities with it.

I spent about 3 to 4 weeks waiting for my dry ferts to come in and all I had was Miracle Grow plant spikes for houseplants. I used them at a rate of about 1 every 3 to 4 days and they didn't bother either the plants or the fish. I kept then hanging in a fish net because they breakdown into some slimy white stuff that will spread all over the tank if not careful. I'd hang them there for a few days and then dump the residual.

I've been wondering about this and you made some good points. I just mixed up some Miracle Grow and dumped it in my grow tank. Shouldn't be a problem because I replace 80% of the water every three days since I'm utilizing a lot of sunlight.

But if there is a problem I'm blaming Jeremy

He DID say try it!!!

Urea to plants is not harmful. In fact the reason land animal produce urea is because it is less toxic that ammonia. Pretty much inert. The waste product from metabolism of proteins is ammonia.

As for the formulation. Do the math on the dosing regimens out there. They don't fluctuate that much in nutrient density from most general use fertilizers.

I have used the shults stuff for several years to grow some great orchids above the kitchen sink.

I think Urea will pretty readily break down into ammonia, so that, combined with the actual ammonia in the fertilizer is probably why it would be harmful for an aquarium with critters in it.

If all it is is plants in the aquarium, I imagine it would work. (I don't think snails really count, they seem to be able to survive almost anything...)

Although I disagree with JeremyM in that I don't think the nutrients are essentially different, they make a good point that the situations/environments of garden and potted plants are quite different from an aquarium. The basic biochemical reactions in all plants are going to be very similar, but depending on the type of environment, different ferts are more or less useful for certain purposes.

I think it should work, but I have no clue on the dosing, but I think you can probably make some pretty good estimates based on what ratios people generally use for heavily planted tanks (and, without the critters, and with the emergent growth, you can probably go a little bit higher as well).

Urea is a stable molecule that is actively broken into ammonia or ammonium by plants and bacteria. You can dose urea to plants, but it would be wise to add the usually not nessesary trace element nickel. Nickel is required by plants to metabolize urea.

I wouldn't use it personally. Your'e likely to end up with an algae farm from the nitrogen sources. The phosphate to nitrogen ratio is backwards as well. Phosphate should be around 17% of total nitrogen. This is roughly 200%!

Just for fun I added this to a nutrient calculator. Here are the results.

Targeting nitrogen...

To raise Total Nitrogen 7.5 ppm in your 10 gallon tank you will need to add 2.84 ML of Schultz 10-15-10 Plant Food plus Micronutrients.





Targeting PO4...

To raise PO4 1.3 ppm in your 10 gallon tank you will need to add 0.25 ML of Schultz 10-15-10 Plant Food plus Micronutrients.

The issue with urea is it is a waste product, and in practice will contain everything that the animals that produced it flushed from their systems as toxins.

I did a little Google search: It looks like urea is commercially produced with no animals assisting.

The urea in organic compost is commercially produced?

Isn't that kinda a contradiction in terms?

EDIT: OH NVM- this is the *other* Miracle Gro & urea thread... lol

Urea, whether organic or synthetic is urea. When added to a planted tank it will rapidly breakdown into NH3/NH4 and CO2. What happens when we add ammonia to tanks with high light? Green water.

If we add urea or Ammoniacal Nitrogen sources the bacteria will process most of it. Sure plants will benefit some but the bacterial populations will simply increase. What's the difference between adding urea or more fish (fish food)? What's the end product of the cycle? NO3.

Plants can store NO3 but cannot store NH4. Seems to me as though plants have evolved to take advantage of the nitrogen sources available. Urea and other Ammoniacal Nitrogen sources provide nitrogen. However, it comes at a cost. I'd rather use a nitrate form of nitrogen and not play on the razor's edge.

The fertilizer in question could be used as a PO4 source. The nitrogen sources seem low enough to not cause significant problems. To be used as a one source fertilizer? No. It simply isn't designed for an aquatic environment.