I recently cleaned my tank and upon looking in one of the buckets that I had set a large lava rock in there were little grey shrimp swimming around. I have found out that they are gammarus shrimp, but that is about all I know about them. Are they good or bad? I also have red and white worms, I think they are both planarians, are the shrimp eating them? Any information about them is welcome.

Thanks,
Amanda

Planaria are normally white but I have some big black ones that I find slink sucking
in the bathtub after water changes. Planaria will remain sucked onto surfaces. If the
worms are wiggling around, they are probably some other kind. There are so many
species though! Most feed on debris and detritus (fish food, dead animals and plants).
Most are harmless. Remember, if they were parasites, they would be inside their
host/victim and can't live outside of them for very long (most kinds). As for the little
shrimp, you have to look at what's in your tank as for where they came from.
Consider everything you've ever added to the tank. If you've ever put in water from
another source (a store's tank, a pond, water with live plants, etc.), then that's where
it might have come from. If you ever put in live plants that were damp, they might
have held some juvenile gammarus. Gammarus are good for fish to eat but fish won't
bother with small planaria. Keeping the tank clean will reduce the planaria numbers.
I'm not positive, but I don't think the gammarus eat planaria. Like most shrimp, they
collect things floating around the tank or settled on the bottom - fish foods, very small
animals and plants. Not knowing more, I don't think the shrimp or planaria are "bad"
but the planaria can get out of hand and indicate there's a lot of debris in the tank
if you have a lot of them. I hope others with experience with these guys will post
a message as well.

The red ones are bloodworms. My gammarus eat bloodworms and planaria.