# Osmocote in the substrate



## Dryn (Sep 6, 2007)

In the aquarium magazines I read, there are several companies that offer products that contain osmocote for substrate fertilization. One in particular shows a capsule full of the little B.B.-sized fertilizer. I had a large can of Osmocote for my terrestrial plants, and I added 1/4 tsp. to my 5.5 gallon planted nano two weeks ago, overtop of a soil layer and under some sultz's aquatic soil. The tank contains five Rasbora heteromorphas, and many plants. Does anyone know why the aquarium companies are using osmocote? (other fertilizers have low P values too) Does anyone think this will effect my fish? (Nitrate are 0 ppm) How much osmocote can one add to their soil if it is a good idea? Can I get some pill capsules and fill them full of osmocote and use it when I run out of fertilizer tablets? (One can of osmocote = $5.00 One pack of 12 tablets = $10.00.)


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## dwalstad (Apr 14, 2006)

Dryn said:


> In the aquarium magazines I read, there are several companies that offer products that contain osmocote for substrate fertilization. One in particular shows a capsule full of the little B.B.-sized fertilizer. I had a large can of Osmocote for my terrestrial plants, and I added 1/4 tsp. to my 5.5 gallon planted nano two weeks ago, overtop of a soil layer and under some sultz's aquatic soil. The tank contains five Rasbora heteromorphas, and many plants. Does anyone know why the aquarium companies are using osmocote? (other fertilizers have low P values too) Does anyone think this will effect my fish? (Nitrate are 0 ppm) How much osmocote can one add to their soil if it is a good idea? Can I get some pill capsules and fill them full of osmocote and use it when I run out of fertilizer tablets? (One can of osmocote = $5.00 One pack of 12 tablets = $10.00.)


Dear Dryn,

Many times I have conducted experiments fertilizing the soil with chemical fertilizers. I too was convinced that if I fertilized the soil, I'd get better plant growth. Again and again, added fertilizers (major nutrients or trace elements) either did not help plant growth or severely inhibited it-- in comparison to unfertilized controls.

One scientific study with Osmocote showed no advantage to aquatic plants, despite this fertilizer's slow-release properties.

Soil alone has plenty of nutrients for submerged aquatic plants, which are almost all slow-growers. They don't require the nutrient levels of many terrestrial plants.

The fishfood you add will replenish the nutrients removed by plants. The only plants that truly need substrate fertilizers are pond lilies and other emergent plants growing in full sun. You will have to read my book to understand why this is true.

Despite what aquarium companies say, added fertilizers can cause problems. Many fetilizers like Osmocote are designed for terrestrial plants. In the terrestrial (i.e. aerobic) environment, the large amounts of nitrates and sulfates they contain present no problems. However, in the aquatic (i.e., anaerobic) environment they can poison plants and fish (nitrite and hydrogen sulfide toxicity).

In the end, your tank might do okay, but I wouldn't waste a lot of time looking for fertilizers. That's just my opinion.


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## Dryn (Sep 6, 2007)

I am honored to be hearing from you. I plan on getting a copy of your book. 

The tank I have the osmocote in is an experiment tank, and so far it hasn't done anything. 0ppm ammonia 0 ppm nitrite and 0 ppm nitrate. None of the plants have grown either. I suspect that this is do to the lack of Carbon. The powerfilter has an extremely high flow rate for that tank and probably is driving off the CO2. I have another 20L densely planted high tech tank in the living room, but I wanted this tank to be for fun. The substrate is organic potting soil topped with schultz soil b/c that is what I had at the time. A 150 watt full spec. power compact desk lamp is its sole lighting. (No uncovered window in the bedroom b/c of my wife). I had some osmocote on hand, hence this thread. Last week I started dosing excel to up the carbon level. Algae has started to creep in and the plants are healthy but not growing. I wonder if the lighting is too much? 27watts per gallon seems like a lot.


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## dwalstad (Apr 14, 2006)

Dryn said:


> I am honored to be hearing from you. I plan on getting a copy of your book.
> 
> The tank I have the osmocote in is an experiment tank, and so far it hasn't done anything. 0ppm ammonia 0 ppm nitrite and 0 ppm nitrate. None of the plants have grown either. I suspect that this is do to the lack of Carbon. The powerfilter has an extremely high flow rate for that tank and probably is driving off the CO2. I have another 20L densely planted high tech tank in the living room, but I wanted this tank to be for fun. The substrate is organic potting soil topped with schultz soil b/c that is what I had at the time. A 150 watt full spec. power compact desk lamp is its sole lighting. (No uncovered window in the bedroom b/c of my wife). I had some osmocote on hand, hence this thread. Last week I started dosing excel to up the carbon level. Algae has started to creep in and the plants are healthy but not growing. I wonder if the lighting is too much? 27watts per gallon seems like a lot.


Good Gracious! I've never heard of using that much light. You may be inhibiting your plants; submerged plants can't use that much, and aquatic plants can be "photo-inhibited". I'd definitely get floating plants for this tank before its taken over by algae.

The substrate sounds fine. It's probably giving off enough CO2 that you don't need to add a thing.

I'd turn down the filter and reduce lighting by 90%.

Glad you are getting my book. Its hard to "re-invent the wheel" for every hobbyist setting up an NPT.


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## Dryn (Sep 6, 2007)

Thanks for the attention. 

My filter isn't adjustable. I built a canister filter but it is too noisy for the location. I thought about adding some duckweed (the LFS gives it away) and I will now. The lamp can only be raised by six inches, but combined with the duckweed, I hope that will be enough. 

I have your book on order at the bookstore. I'm always looking for different things. It is a hobby after all!


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## j_m_lizard (Oct 16, 2007)

I suspect thatthe "250 watt" desk-lamp is actually a 27 watt lamp which gives off "the equivalent of 150 watts of incandescent light." Again, this is just a speculation, but I do know that is what the 27 watt desk lamp at Home Depot claims on the package, and it may have caused some confusion.

-Jared

ps - It is an honor to be in on the same thread as you Ms Walstad. I love your approach to the hobby, and the results it can produce in a properly set up and maintained tank. Furthermore, I think your participation in forums like these is just a testament to how much you care about other's success and enjoyment in this hobby as well.


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## Dryn (Sep 6, 2007)

This is true. It is unclear to me whether the WPG rating for plants is based on output or input. Most flourescents don't come with an easily identifiable output wattage. The lamp is a power compact flourescent anyway, so it is that much harder to rate a WPG for it. It is however, very short. It only really lights up 80% of the 5.5 gallon tank. The sides are relatively shadowed. (the room is absolutely dark, so it is easy to see its illumination factor). That said, it is still way too much light for such a shallow, small tank.


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## Dryn (Sep 6, 2007)

I am going to have to take down this little tank. I believe that the osmocote in the substrate has done nothing. The lighting was just way too powerful. The plants are failing, and their decay has let the algae prosper and thus, deteriorating the water quality to the point that some of the fish have died. I'm going to defer to dwastad and not use it again.

I think I am going to get a smaller light and retry using eco-complete substrate and a home-made yeast factory, just like my other tank.


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## aquabillpers (Apr 13, 2006)

Hi,

It's too bad that your tank isn't working out, but that has happened to most of us. Starting over is often the best thing to do.

In the new tank, why not try setting up a Walstad-type tank, with soil covered with gravel, reasonable lighting, and no extra CO2? Such a tank would be easier to set up and run, be less costly, and produce great results.

Good luck!

Bill


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## dawntwister (Sep 29, 2007)

Yey try the Walstad-type tank method. It is less complicated. If you can't find pebbles the right size try pool sand. All of my plants are flourishing in substrate with organic top soil, $1, topped with pool sand. I just occasionally dose with leaf zone. For lighting I just have 2 floresant screw bulbs and indirect sun light. Even got java fern and christmass moss producing shoots. You don't need to make things so complicated.


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## Dryn (Sep 6, 2007)

thanks


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