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Hi,

I have a 29G well planted tank that has between 2 to 3 inches of gravel (small). The lower half
is a mixture of 50% gravel and 50% Aquarium Pharmaceuticals First layer Pure Laterite.

As I understand, the Laterite would be used up by the plants over time. Now, if this is right, then
what is the time frame until I would have to start to supplement with other fertilizers, like tablets?
I used to add some Flourish, Flourish Excel, and Flourish Iron to the water on a weekly base for the
first 3 months, but have since cut it out as I have not seen any change in plant conditions.

In case it matters, I have 40W of lighting and an average arrangement of plants, from Green Cabomba
to Ludwigia (Repens), with a tendency to fast growing plants. The tank has been set up 4 months ago.

Thanks,

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

Ingo,

Eventually, if nutrients are only removed from the system(through water changes and clippings), the laterite's usefulness would expire. However, if you are able to dose liquid ferts the laterite will last much longer, and if you put plant spikes near the roots of your plants the laterite will last even longer. Some plants like echinodorus species do better if you put in a plant spike anyways, while fast growing stem plants take a lot of nutrients from the water column and liquid ferts are appreciated. Just don't add too many ferts because an algae outbreak could occur. It's best to dose too little and work your way up to a full dose IMO, over a period of weeks to view the plants' response to the ferts.

matt

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Critical Fertilator: The Micromanager of Macronutrients

Any idea on the length of time until the substrate is depleted (assuming no ferts, plant spikes, and disregarding fish detritus)?

Well I'd say it would last a while. I'm thinking a year or two, but I can't say that for sure. And it depends on what types of plants, how many, and their growth rate. I've read somewhere(I've read from too many places that I can't keep 'em straight) that with the proper support, the laterite/flourite/eco complete or whatever can last indefinitely. I don't think that a nutricious base can do the job alone anyways. I'm pretty sure that some plants can't get everything they need from these sources and need extra ferts if they are growing fast enough to use what's in the tap(say with a lot of stem plants and co2 injection). It's best just to monitor your plants to see what they need though. They will tell you if they can no longer get nutrients from the gravel bed.

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Critical Fertilator: The Micromanager of Macronutrients