How to "Fix?" my substrate



My substrate is all purpose gravel completely free of nutrients. I use liquid ferts but after reading this website liquid ferts are only half the battle. Is there anything I can do to fix my gravel without emptying my tank pulling up all my plants and changing the substrate?

I read somewhere that you can make nutrient rich clay balls and shove them down by your roots? Where can I find information on how to do this or is there something better that I can do? changing my substrate is out of the question simply because I can't afford filling a 90 gallon with ecocomplete.



Lifetime Charter Member
Lifetime Member
Nov 21, 2007
Los Angeles, CA
No matter which method you are using for your tank, i.e. non-CO2 or CO2, you should be able to get by with your current gravel. I have one small (10G) with inert gravel and my plants are doing fine -- it is a non-CO2 tank. I am dosing very small amounts of KH2PO4 (mono potassium phosphate), KNO3 (potassium nitrate) and Tropica Plant Nutrition (TPN) micro nutrients. Also, since I am not doing water changes in my non-CO2 tanks, I dose a little Seachem Equilibrium occasionally to keep the calcium, magnesium, and other minerals in the tank.

In my other non-CO2 tanks, I have Seachem Flourite substrate, which is nothing like an ADA Aqua Soil or Eco-Complete. As far as I know, the main thing Flourite has going for it (that an inert gravel doesn't) is iron. If you are getting iron in your fertilizer (TPN has it), I think you'll be fine with inert gravel as your substrate.

There are several posts in the Articles forum that can help guide you on fertilization, depending on which method you are using.


Lifetime Charter Member
Lifetime Member
Jan 24, 2005
Sacramento, CA
The best of both worlds approach is the best - a substrate that is fertile, and the water column dosed with fertilizers too. But, plants will grow well with only the water column fertilizing. Just because an aquatic plant has good roots doesn't mean it has to get root fertilizing. Roots are there for other reasons, to hold the plant in position in flowing water, to feed the plant during dry seasons, etc.

One way Tom suggests for clay balls is to mix some "mud" with a little fertilizer, using KNO3, KH2PO4 and traces, not terrestrial fertilizers, then pour the mx into an ice cube tray and freeze it. Just poke a frozen mud ball into the substrate, down deep, and you have a fertile substrate. You also have mud in the substrate which might some day be pulled up if you pull up a deeply rooted plant.