This Swamp Tank idea is very interesting. I've been really interested in starting a brackish tank, really small, for a couple of bumblebee gobies (which aren't even available---my plan is to beg the store to order them for me when I'm ready). I did get a fantastic mangrove goby from a nearby brackish gulch (I live on Maui), but returned it the next day because I couldn't figure out how to filter the water when it was so shallow. (It's a great fish. Ate right away, and glared at us with a lot of character.) Can you explain what you mean by "hooking up a pump"? Also, can anyone help me with adjusting my water? I have to use rainwater, and it's VERY SOFT and LOW pH and LOW alkalinity. The goby's gulch water was just the opposite; but there was water coming in from above, where there's a lot of sugarcane fields, and fertilizer. I read somewhere about using shells or coral sand in the filter itself. How do you do that? I've really tried to understand all those chemistry articles, but I'm having a hard time. I took a lot of biology in school, but not chemistry.