Fish Capacity For A Reef Tank

[Grey Guy]

Some of us remember the days when live stock was measured by inch per gallon. Fresh water was higher than salt water. I found on a web site calculator that my 120 gallon tank could accommodate 24 inches of fish. That's only 8 fish 3" long. That sounds about right to me. I have always been astounded by the number of fish in one tank at the Local Fish Store. I figured since the fish were being bought or moved around, that the LFS could get away with it.

In recent years, now more than ever I see privately owned aquariums so loaded with fish, that it looks like a swarm of activity. What has changed to make loading up a fish tank, so doable?

 

[Dylan Grech]

I would argue that filtration methods have improved a lot. Roller mats, super efficient skimmers, bio balls, carbon dosing, and many more can take up a much bigger bio load then filtration systems of 10yrs ago.

On the other hand I would also argue that too many fish could have territory issues and general agression.

I would say use your formula but if you want to go 20-30% over that you should still be fine if the tank can handle the bio load.

 

[Grey Guy]

Well said. Thanks

 

[lariat8099]

Very well said. I'm about 35% over and my SPS tank is thriving

 

[Grey Guy]

That is awesome. How long have you had your current setup?

 

[Salty1962]

I think with new technology and husbandry practices, we can push it a little more as long as compatibility is taken into consideration[emoji6]

 

[enveetie]

I agree with the above explanations but also want to add that "rules" and guidelines also change based on accumulated anecdotal evidence. Our hobby is awash in anecdotes and as more and more people add their two cents on sites like these a general consensus is formed and common belief guidelines change.

For example, I've been reading a lot on housing more than one pygmy angel and as you read up on posts from 10 years ago, the consensus was it cannot be done. Posts dated more recently for the most part report positive results. The attitude slowly changed as more and more people tried it and reported on it.

As for crowded marine tanks, I think the idea of overwhelming numbers to distribute aggression has a lot to do with the success, again, an idea that is more recent as people push the envelope more and more over tanks of 10-20 years ago.

 

[Grey Guy]

You make some good points, especially about crowding and aggression. Makes sense. Never thought of it that way, but in a crowded tank it does look like no one knows who to pick on.

 

[FFFishy]

The correct answer is probably, "It Depends". Here's my personal experience . . . .
120 Gallon DT (4ft x 2ft x 2ft) started mid-June 2014, so just a bit over 3 years old.

My current Fish List with 'maximum length' (data from various sources):
Banggai Cardinal (3")
Ocellaris Clown (2 @ 3")
Lyretail Anthia (2 @ 4")
Diamond Watchman Goby (5")
Coral Beauty Angel (4")
Blue Flasher Wrasse (3")
Yellow Eye Kole Tang (4")
One Spot Fox Face (5")
Solorensis Wrasse (5")
Royal Gramma (4")
Lubbock's Fairy Wrasse (4")
Helfrichi Firefish (4")

So I'm at a 'maximum total fish length' of 55 inches. The list is in the order that the fish were added to the DT. Over the past year, I've lost (without a trace) one Banggai Cardinal and one Lyretail Anthia. I do not intend to add any fish. My DT is not crowded. Each of the fish seem to have their own hiding places at night. The only aggression that I observe is that the One Spot can be quite a hog at feeding time. My DT is clean, decent parameters (nitrate 2-3, phosphate .04-.05). There's a nice level of fish activity throughout the tank.

Do I have too many fish? I think I'm right at the limit. I don't want to add a fish and upset the balance.

I wish I had a larger tank and am considering upgrading to a 6 foot long 180G. I hesitate though because what I've got is working very nicely. And, with an upgrade to a 180G, all I could add to my existing fish list would be 2-4 fish in the same size range.

 

[Willragan]

Varies. Needs to be a balance. Less fish less water changes more fish more water changes. Different corals tolerate different nutrient levels. No single answer.

 

[Willragan]

Many variables

 

[Willragan]

Take ur best guess at safe max and do half that. Lol