This idea came about one day while discussing reef diversity with Dr. Ron Shimek at his Marine Depot Forum. He thinks that one of the problems we face as reef keepers is that over time, the number of species that are in our tanks decreases.

In some ways, this is natural- one species takes advantage of conditions and outcompetes other species in the same niche. Unlike the oceans, however, there's no tide to wash in new species in our tanks. That means we need to pay attention to the species in our tanks and replenish them from time to time.

To that end, I came up with what I hope is a useful tool for evaluating the diversity in your tank / refugium. I didn't actually arrange the items in the above card in any kind of order, such that a particular column or row would constitute a biologically diverse group of critters. Realistically, if you can identify ten or twelve items from the above card, you're probably good.

So what do you do if you can't identify enough species? You could get a cup of sand from someone else's refugium, if you trust that they don't have any pests. You might also get some chaeto from someone else- it often houses many different species of 'pods. Another strategy is to get a chunk of uncured live rock or live rock rubble from a fresh shipment at your LFS. There are also sites that sell detrivore tune-up packages; the two that Dr. Shimek identified are Inland Aquatics and Indo-Pacific Sea Farms.

Below are some links and pictures of critters in the grid.