Silly question about how many fish a tank can support

[Leaellynasaura]

I have a 135 gallon mixed reef. I have currently 2 female mollies, 2 banggai cardinals, 2 clowns, 1 yellow tang, 4 blue/green reef chromis, handful of snails and about 15 hermit crabs.

The mollies gave birth and I am raising about 30 of their young in a separate tank. They babies are about 1 inch long now and soon they will be ready to be put into the big tank. Can I put all 30 in if I want? I have a small deep sand bed in the filter loop and my nitrates always read zero currently.

 

[Maggie321]

If it were my tank I'd trade the mollies at the LFS for something. Keep some, but trade the majority...

I have heard with saltwater it's 1" of fish for every 2 gallons. Not sure how accurate that is. It probably depends on how much filtration you have and frequency + volume of water changes.

 

[4FordFamily]

I have a 135 gallon mixed reef. I have currently 2 female mollies, 2 banggai cardinals, 2 clowns, 1 yellow tang, 4 blue/green reef chromis, handful of snails and about 15 hermit crabs.

The mollies gave birth and I am raising about 30 of their young in a separate tank. They babies are about 1 inch long now and soon they will be ready to be put into the big tank. Can I put all 30 in if I want? I have a small deep sand bed in the filter loop and my nitrates always read zero currently.

I’m not sure I’d want a bunch of mollies but you could, I guess, for some very short amount of time. That’s a lot of mollies.

Total capacity of fish is a function of husbandry, nutrient exportation (skimmers and other reducing equipment or methods), age and stability of tank, and type of fish — among many other things.

 

[Amps Reef Life]

I’m not sure I’d want a bunch of mollies but you could, I guess, for some very short amount of time. That’s a lot of mollies.

Total capacity of fish is a function of husbandry, nutrient exportation (skimmers and other reducing equipment or methods), age and stability of tank, and type of fish — among many other things.

Exactly this!!!!! I would recommend searching this topic on this forum. There are a lot of post about it. You want to think about any fish adulting into full size as fish grow they can become more aggressive depending on the environment they are kept in. Fish will act out when they aren't comfortable. You could maybe keep all those mollies but think about the future you may want some other fish. My opinion is that the one to two-inch fish rule doesn't apply to saltwater tanks.

 

[bblumberg]

As 4FordFamily noted, how many fish you can keep depends on your nutrient export and ability to keep conditions within a range suitable for whatever corals you want to keep. Mollies are prolific and can easily multiply to crazy numbers. Don't think that you are safe without males in the tank because mollies and other livebearing fishes store sperm from a mating and can use this to fertilize multiple batches of eggs. We had mollies in a fw tank years ago and could never find a LFS that would take mollies for free, let alone purchase them.

If you want to keep a decent amount of fish, I'd consider adding media to your sump that will reduce nitrate to N2 gas. I like Siporax for this purpose but there are many other possibilities. Keep up with your nitrate measurements and don't let levels rise past about 5-10 ppm if you want to keep SPS. Also pay attention to phosphate levels and try to keep them around 0.05 ish ppm.

Bruce

 

[PatW]

With vigorous and zealous husbandry, an aquarium can support quite a few fish. But if you do that, you are leaving yourself not much margin of error. A power failure or other ill chance can quickly turn into a tank crash killing everything. I figure about one fish to 10 gallons.

Mollies are starter fresh water fish. They add to the bioload just as much as the others and reduce your safety margin. It is more conservative to remove them.

 

[Leaellynasaura]

I know that male mollies can be very aggressive. My hope is that if I have enough of them they will cancel each other out. Kind of like when you see videos of like 100 cats together. There are so many they can’t fight.