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substrate fertilization

It's been a while since I last contributed, so let me start with my aquarium.  My setup is a three year old, heavily planted 55 g tank.  The plants are the easier to grow types.  I have canister filtration with CO2 injection.

Now I believe gardening is much like music.  The best growers have a “green thumb”.  The rest of us have a “tin ear”; commonly called a “brown thumb”.  Those with a “green thumb” seem to have an instinct for adding the right amount of fertilizer at the right time and place.  Those with a “tin ear” (brown thumb) have to learn to play from the printed page.

Discussions on the substrate have been going on since long before I joined this list.  How much and with what do you fertilize the substrate?  There are two answers to this; one for those with a green thumb and another for those with a tin ear. For those with a green thumb, it’s simple, fertilize the substrate and grow beautiful plants. The alternative to this appears to be, don’t fertilize the substrate at all!  Having a “brown thumb”, I can testify that the answer to substrate fertilization has never been sufficiently answered for me.  How much do I fertilize?

Three years ago, I planted my aquarium.  I had researched the archives and learned as much as I could from the knowledgeable.  The predominate philosophy seemed to be, start with a good rich substrate and fertilize the water column.  So I used sand with a high soil content, added lauterite and additional fertilizer (water plant type).  My lighting was 160 w fluorescent.  I measured pH, nitrate, iron, calcium, hardness, phosphate, etc. and regularly changed water and used RO water (with adjustments as necessary).

Early on I could control the water column and thereby control algae.  However at about the age of 2, I had lost control of the water column.  The nitrate concentration started to rise, the phosphate concentration began to rise and the algae began to take over.  Even with zero nitrate input, the fish were still supplying enough ammonia to raise the level of nitrates.  The only way to control the algae was to lower the light by ˝.  This reduced the growth of the algae but also reduced the plant growth.  

We had some discussion on the list about a year ago and the only logical answer seemed to be that the plants were not taking their nutrients from the water column because they were getting everything they needed from the substrate.  My substrate was just to good!  I’ve let it run an additional year and I’ve not found a better answer.  I am not able to get a good healthy plant growth without excessive algae.  So I am getting ready to tear it all down and start again.  This time I am going to wash the sand until there is on soluble nutrient left and fertilize only the water column.

Fertilizing the substrate is probably a better way of producing a well planted tank but for those of us who cannot judge the right amount of “stuff” to put in it, the next best solution appears to be don’t fertilize the substrate at all!  This way I can rely on tests to tell me the state of the tank and I can add nutrients as needed to the water column.  It is generally agreed that if you control the water column, you control the algae.  If a small amount of water flow is made through the sand, it should be possible to control the water conditions and provide adequate fertilization for the plants.  Anyway, I will let you know how it works…in a year or so.

Best regards,
K5vkq at ix_netcom.com