true eco-system

Question
Hi, at the moment I have a 400L tank i am setting up. Because I am wanting to create an Eco-system and not a habitat i so far have 2 adult and 30 juvenile Physa snails to eat algy and solid excretions, 2 adult Hyridella mussels to filter the water, aprox 200 Nematode worms to live in the stone/sand layer. I am also looking at getting some (30) non-blood sucking leaches. I also use an oxygen stone to balance the water pH. at the moment I am growing algy in a separate tank to feed the snails, also at the moment my tank and water quality is perfect. my question to you is this. What plants and fish including numbers should I introduce to maintain this balance, also what alterations should I make to my current bio-filters to accommodate the increased load. Kind regards Andrew

Answer
Hi Andrew,

The Physa snails, mussels, worms, and leeches (non-sucking) would not affect the fish whatsoever, regardless of the type. When you mean, "a true eco-system", do you mean that you will have a self-sustaining tank without the presence of filters, etc? If that is so, you would only be able to add a limited amount of fish, because two mussels will not provide enough filtration to support a large fish population.

If I'm mistaken, and you DO have filters, then you could add a large amount of fish. You do not need to make adjustments to your bio-filters, rather, by adding fish slowly, 2-4 per week, you will slowly build up the population of beneficial bacteria. This bacteria will develop in your tank, and they will remove ammonia (produced by decomposing fish waste), and turn it into harmless substances. It is important to have a filter, because the bacteria will populate the filter, as they are aerobic organisms, meaning they need lots of oxygen. (the filter has lots of oxygen, due to water movement within)

I do not know what category or general group of fish you are leaning towards, and there are endless numbers of suggestions possible. If you are looking for interesting but useful fish that would benefit your system, I've suggested a few below.

-Plecostomus (These do well in a tank your size, they earn their keep by eating algae)
-Otocinclus (These are best kept in a small group, and will also eat algae)
-Catfish (Corydoras, various species, are bottom scavengers and will eat sinking food)


And of course, here are some of the colorful, common, and attractive freshwater fish that are extremely popular:

-Swordtail
-Zebra Danio
-Tetras (Neon, Rummynose, Serpae, etc.)
-Barbs (Tiger, Cherry, etc.)
-Angelfish
-Gouramis

Remember to stock fish slowly, and add only 4 or so each week. Performing 10% water changes twice a week during the first month will help reduce and dilute any toxic compounds that commonly develop during this period.

For plants, I would recommend the following species:
-Java Fern
-Java Moss
-Hygrophila Polysperma (Hygro)
-Wisteria
-Anubias (various)

The number of plants you want depends on the way you want your tank to look: Lots of room for fish (in other words, a bare tank) with the occasional plant, or maybe a forest?

I would add a few bunches of plants, and they will reproduce eventually and cover your tank.

I hope this helps, and Happy Fishkeeping!