Freshwater Scuds: The Ultimate Algae Eaters?

Algae is the bane of most freshwater aquarium keepers. We've all had it at some point and many of us continue to struggle with one for or another for long periods of time. No doubt algae has been the reason some have gotten out of the hobby entirely. In my case, I've had to deal with hair algae, staghorn algae, and black beard algae.

I've had success controlling staghorn algae with Seachem's Excel, but I'd rather not have to use such chemicals all of the time. I've been able to knock out hair algae using API's Algaefix, which is harmful to shrimp so not a perfect solution. As for black beard algae, I've found nothing more effective than hydrogen peroxide, but I've never been able to eliminate it entirely and who wants to do treatments every day?

Enter the freshwater scud. These little guys sit at the bottom of the food chain and eat decaying plant matter, left over fish food, and algae. In fact, some testing suggests that if given a healthy plant with algae, they will eat the algae and ignore the leaf. Need proof? Take a look at this before and after shot of an anubias leaf I left in a container of 50 or so scuds for 24+ hours.

Anubias Leaf Covered With AlgaeAnubias Leaf Covered With Algae
Anubias Leaf After Scud CleaningAnubias Leaf After Scud “Cleaning”
BBA in Bottle Cap: Before and 24 Hours After Introducing Scuds

Some other things I've tested:

  1. Scuds seem to be unharmed by Seachem Excel dosed up to 1.75x the standard dose. I haven't tested higher amounts so they may be able to tolerate more.
  2. The scuds cleaned off algae from Lobelia Cardinals “Dwarf” without harming the leaves. I was curious about this because these leaves are sofware than those of the Anubias in the above photos.
  3. The scuds had no problem eating the algae off of wood. Once the algae was gone, the scuds moved on.
  4. Scuds will eat the “leaves” of java moss leaving the stems behind. They eat it slowly though so it's possible the moss will grow fast enough to stay ahead of them.
  5. The overnight temperature that I've confirmed scuds can handle is 2 degrees celsius.

These are things I've read about scuds that I haven't yet verified for myself.

  1. Pygmy Sunfish are good fish for keeping a scud population in check.
  2. There doesn't seem to be a way to kill scuds that won't also kill fish and shrimp. However, some claim that using seltzer water (equivalent to a high dose of CO2) will kill scuds while not killing plants. This sounds promising since it'd be safer than using chemicals that might remain in the tank.

My hope is that I can introduce these scuds directly to my planted aquariums. However, I'm trying to find answers to the following first:

  1. Will the scud population control itself based on the amount of food available? Will the fish keep the scud numbers in check?
  2. Do scuds “prefer” certain foods over others i.e. will they eat algae and decaying plant matter first? Are there some live plants that they can't resist? There are reports that scuds will eat moss.
  3. Do scuds attack young, adult, or moulting shrimp?
  4. If needed, is there any way to eliminate scuds entirely from an aquarium?
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