Fertilizer

Plants need nutrients to grow.

The unfortunate thing about fertilizing this way is that all these nutrients are available to the algae as well. If all this digested food could be kept deep in the substrate, the plants would have a much easier time getting at it than the algae. For this reason I prefer to feed my fish VERY sparingly and to use a solid fertilizer in the substrate. I have used "Lilipons" brand pond lily tablets with great success (after having tried many made-for-aquarium additives which weren't as good and are generally overpriced).

I break the rather large tablets into 8 or 16 smaller pieces (best accomplished by placing a flat-head screwdriver onto the tablet and striking with a hammer) and push them deep into the loam/vermiculite part of the substrate. This helps keep the nutrients out of the water and near the roots. I would use no more than one whole tablet when you first plant the tank, and then add more after making sure the nitrate levels in the tank haven't risen above 5 ppm (see algae and test kit sections).

Plants also require plenty of iron. The "Lilipons" tablets contain iron, and this is probably enough. However, I am paranoid and I have been occasionally adding aquarium trace element additives (they contain chelated iron and some other important micronutrients which are usually supplied in tap water, and are somewhat overpriced) or garden supply iron ("Security" brand iron plus chelate; about 30 granules per day in a 55 gal.; $5.49 at a local hardware store for a lifetime supply).

My paranoia stems from a tank I had set up with only a coarse substrate (no Yolo loam) into which I had put some of the lily tablets. Plant growth really took off for about 3 weeks after the fertilizer tablets were added, but suddenly all the plants began dying. When about 3/4 of the plants were looking pretty sad, I began adding iron daily and all the plants that hadn't completely died put out new shoots and came back nicely. Presumably the roots could not contact the iron in the tablets well enough to absorb it without the fine loam, or there was too much water circulation through the substrate. Anyway, I think the tablets would probably supply sufficient iron (in the presence of clay) to keep the plants happy, but I haven't verified this.

By the way, even tap water contains soluble iron, but in the high oxygen environment of your aquarium it quickly turns to rust which the plants cannot use. Chelated iron doesn't oxidize quickly and so will remain available for weeks. (Note that "Security" brand is only 0.25% chelated iron, the rest is unchelated and quickly turns to rust, so I add it every night before bed (since it temporarily slightly clouds the water) hoping that some of the unchelated iron has a chance to be absorbed too.

Finally I would like to warn against using the cheap tree fertilizer available in garden supply. A friend tried this not noticing that there was chlorine in the ingredients, and subsequently killed all his fish. Try the Osmocote tablets described below. In summary, I would add some solid nitrogen containing fertilizer in the substrate (especially Lilipons or similar), check for high nitrates (if they're high (above 10 ppm), stop fertilizing with nitrogen and increase water changes until they lower), and add chelated iron if the plants take a turn for the worse. For comparison with other fertilizers, here are the Lilipons ingredients:

Lilipons Planting Tablets

• 20% nitrogen (7% soluble, 13% insoluble)
• 10% phosphoric acid
• 5% potash
• 2.6% calcium
• 1.6% sulfur
• 0.35% iron

          Van Ness Water Gardens
          2460 North Euclid Ave
          Upland, CA 91784-1199
          909-982-2425
          Fax: 909-949-7217

A tablet with the EXACT same ingredients and proportions was available in the tree fertilizer section of our local hardware store. It's called "Osmocote (Agriform) Planting Tablets" and are about 1/3 larger than the Lilipons for $0.35 per tablet. This seems like a more convenient source, since Osmocote is a big company so these should be available most places. If not, call Van Ness.

(Note: The addition of phosphates and sulfates to the aquarium is not above controversy. I have used these tablets in tanks with NO visible algae growth and without any apparent harm to roots from hydrogen sulfide gas. All I can say is that it works, despite the theory. These tanks have been set up less than one year.)