Kessil

Thoughts on saltwater mollies in a reef tank?

Fish Boss

Fish Boss

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Hey everyone, I read recently about how mollies are used to see if fish or entire aquriums have disease. The idea is you take a freshwater molly, slowly acclimate it to saltwater, and then add it into a quarantine or aquarium. Since the fish shouldnt have any resistance to saltwater pathogens, it should get sick if there are pathogens in the environment.

I got my tank for free on FB marketplace. It had been up and running for about 5 years, and the included sand was extremely dirty. I separated the sand into different small containers, and thoroughly rinsed it with tap water until it was very clear. Let it sit outside for a few days until it was thoroughly dry. Also bought a lot of used dry rock, and used some of my old dry rock. I dont think there should be any pathogens in the tank, but I want to be as precautious as possible, so I’m going to acclimate a freshwater molly and see if it gets sick at all. If all goes well, I think I will keep it as a permanent tank citizen. The algae grazing aspect is great, and the live bearing/live food is a great idea as well, I think.

What are everyone else’s thoughts/experiences with keeping mollies in a saltwater aquarium?
 
I’ve not heard that they are useful as a “canary in the coal mine” for being more susceptible to saltwater pathogens. The logic doesn’t really make sense to me but I don’t know if it actually is the case or not. Lots of people have been able to adapt them and use them as algae eaters that don’t require a large tank volume, so that part checks out at least. Kenny @under_water_ninja at High Tide Aquatics has had groups of them he conditioned to saltwater, you could ask him if he has available now. He can also probably give you good advice about your other concerns regarding fish diseases.
 
I’ve done it years ago. Here’s what I remember. There are only certain types that you can convert to saltwater. I don’t remember which ones. But it was a lot of work. Slow work. The black ones will show ick easier to see. Once they are shown signs of ick. They are useless to show ick again as they have been infected. Thus your canary.
They are not strong swimmers, so a real reef aquarium flow isn’t really suitable.
They are great sump fish where flow is slower and they eat all the junk that your other fish refuse to eat.
 
I used them for the opposite reason. To cycle with a fish that could not possibly have saltwater disease. Start with a 5 gallon bucket full of freshwater, a heater, and a small pump/air stone. Dump a quart of freshwater and replace with tank water. So it 1 or 2 times a day until the bucket gets close to the aquarium.

Long term mollies are a pita. They reproduce like crazy. They get huge in saltwater. The female die in child birth blocking overflows if not careful.
 
Mine filled my sump with babies.
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under_water_ninja said:
They are great cleaners! They eat ditritis and graze on algae! And they are cheap! I do have about 3 or 4 black ones coming out of quarantine on the 9th. Yes I over quarantine the mollies. Anything that enters my fish sales system has to go through my protocol
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Were your mollies acclimated from freshwater, or did they come in from saltwater?
 
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