As far as fertilizers go, I agree with Azhael on being skeptical in terms of adding chemicals to the tank...you can however, buy certain substrates that are specifically designed for plants tank that can be amphibian friendly.
"A solution is to use a plant-specific substrate, such as Flora Base, by Red Sea, which is especially designed for supporting plant growth. It has the following benefits:
- It's small and soft so no impaction risk.
- It doesn't adversely alter the water chemistry.
- It's easy for rooted plants to get established in.
- It contains nutrients for plant growth.
- It doesn’t contain toxic substances.
There are several different types of plant substrate on the market, but not all are appropriate for an axolotl tank. When choosing one, ensure that it fits the above list of considerations.
Plant-specific substrates are not cheap - Flora Base is about AU$70 for a 5.4 kg (12lb) bag and the other choices are very similar in pricing. That doesn't go far in a large tank since you aim to lay an inch thick of substrate cover over the base of the tank. Though it is expensive it will promote much better plant growth and provide a safe and attractive base to your tank.
When laying the substrate, follow the manufacturer’s instructions. If you’re keen to save some money and have a reasonably clear idea of where you will be planting rooted plants in the tank then you can place areas of sand down in the space where there won’t be any. This way, when you’ve finished laying your substrate you’ll have a bit of a patchwork between the sand and the plant substrate - quite an attractive effect in its own right. "
From
Axolotl Sanctuary
