In theory when looking at a tank of any size, there’s a limit to the amount and size of fish you can put in it. However, I feel as though a lot of tanks can be “overstocked” and as long as parameters remain stable and the fish are happy, this is negligible. I’d like to get some more opinions on this, what would you all consider overstocked in a tank and is there room for this in all tanks? Do you feel your tank is overstocked? Thanks!
What makes a tank overstocked?
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Miami Reef
10K Club Member
When there is overcrowding.
Nemo&Friends
Well-Known Member
When there are not enough hiding places for each fish, which causes stress and increases aggression or even diseases.
Anemone_Fanatic
Valuable Member
Three things.
1) Nutrients are getting too high, too fast.
2) Fish are too crowded in, leading to stress and aggression.
3) When the tank is too full to look nice.
Obviously the third one is subjective, but I still factor it in. The temperaments of individual fish and the quality of the filtration systems vary, which is why "x inches of fish per x amount of gallons" isn't a good rule. There's too much variability.
1) Nutrients are getting too high, too fast.
2) Fish are too crowded in, leading to stress and aggression.
3) When the tank is too full to look nice.
Obviously the third one is subjective, but I still factor it in. The temperaments of individual fish and the quality of the filtration systems vary, which is why "x inches of fish per x amount of gallons" isn't a good rule. There's too much variability.
Jekyl
GSP is the devil and clowns are bad pets
Every fish in the tank should have its own individual hiding / sleeping safe place. If you dont have enough rocks/space to provide that, you're overstocked. Big reason I can't stand NSA tanks. They're not good for the fish, just egos.
00W
7500 Club Member
These are all good answers and you will get many if everyone chimes in.
It really is debatable as to size of fish, how fast they grow, size of tank and personal choice.
I believe in one fish per foot of tank so I have 3 fish in a 4 foot tank and one in a two foot tank.
But that's just me.
Some might think that is silly but I've always done it that way. Lots of rock and a few fish.
If you look through some of the members tanks you'll get a good/better idea of what you might want to accomplish.
@Jekyl said it well.
It really is debatable as to size of fish, how fast they grow, size of tank and personal choice.
I believe in one fish per foot of tank so I have 3 fish in a 4 foot tank and one in a two foot tank.
But that's just me.
Some might think that is silly but I've always done it that way. Lots of rock and a few fish.
If you look through some of the members tanks you'll get a good/better idea of what you might want to accomplish.
@Jekyl said it well.
o2manyfish
Valuable Member
I like lots of fish - Hence the screen name. While I have a real big tank now - 750g - I already have about 150 fish in the tank. I like little fish so there are lots of what I call doinker fish in the tank. But that's not to say it's all small fish - 3 yellow tangs (Adults), 3 Purple Tangs (adult), 6 hippo tangs, Sailfin tang (Adult), Flame tip tang (juvenile), Lavendar tang (juvenile), Achilles (Adult), Powder Blue (Adult) - Some medium sized angels. And from that size all the way down to a 3/4" clown goby. Nobody is getting their butt kicked. I find that even with aggressive fish within chaos you find peace. There are so many fish to chase that they just don't bother.
Some 'think', and I say 'think' because they have no actual experience with it, that 100 fish in a tank is way too many and unhealthy. In our prior 400g tank we had 140 fish - Including the same purple and yellow tangs. In that smaller tank we had a bunch of large angels as well. And at one point in that tank we had the following fish spawning (all at the same time) - Clowns, Bangai, Orange Tail Damsels, Frimandi, Golden Angels (Trio), Joculator Angels, Bellus Angles (Trio), Venustus Angels (Trio) and Goldflake Angels. That's a lot of fish to be happy enough to spawn in captivity. And some of those fish had never even been filmed spawning in captivity at that time.
Now in my many years of loving lots of fish, I didn' think I would ever hit a '2many' point. But in the 750g right now, from a visual standpoint, I think I have too many fish. There are still alot of fish I want to add to the tank to give it more life. But at the moment I think there are too many mid water column fish. There are almost 40 anthias, a dozen chromis almost 10 mollies that the wife wanted -- I don't mind the mollies - they are great algae eaters - but there are too many now for them to be cool.
The question is what am I going to do about it. I can easily see myself getting past 200 fish in this tank. But the mass of mid tank swimmers makes spotting all the lil subtle fish just too difficult. So I think I'm going to start whittling down the Anthias and the chromis.
Fish I still want to add to the tank are a trio of Golden Angels, a pair of yellow belly regal angels, more damsels, Borbonius, trio of gem tangs, more yellow tangs, 24+ Barnacle blennies, another dozen fire fish, so dragon faced pipefish, a pair of Joculator angels, a dozen assorted captive bred pseudochromis and the list goes on. We have 1 juvenile goldflake angel in the tank now, with a second growing up in the outdoor frag tank. Another few months are we will put the two of them together and hopefully have a new pair.
Dave B
Some 'think', and I say 'think' because they have no actual experience with it, that 100 fish in a tank is way too many and unhealthy. In our prior 400g tank we had 140 fish - Including the same purple and yellow tangs. In that smaller tank we had a bunch of large angels as well. And at one point in that tank we had the following fish spawning (all at the same time) - Clowns, Bangai, Orange Tail Damsels, Frimandi, Golden Angels (Trio), Joculator Angels, Bellus Angles (Trio), Venustus Angels (Trio) and Goldflake Angels. That's a lot of fish to be happy enough to spawn in captivity. And some of those fish had never even been filmed spawning in captivity at that time.
Now in my many years of loving lots of fish, I didn' think I would ever hit a '2many' point. But in the 750g right now, from a visual standpoint, I think I have too many fish. There are still alot of fish I want to add to the tank to give it more life. But at the moment I think there are too many mid water column fish. There are almost 40 anthias, a dozen chromis almost 10 mollies that the wife wanted -- I don't mind the mollies - they are great algae eaters - but there are too many now for them to be cool.
The question is what am I going to do about it. I can easily see myself getting past 200 fish in this tank. But the mass of mid tank swimmers makes spotting all the lil subtle fish just too difficult. So I think I'm going to start whittling down the Anthias and the chromis.
Fish I still want to add to the tank are a trio of Golden Angels, a pair of yellow belly regal angels, more damsels, Borbonius, trio of gem tangs, more yellow tangs, 24+ Barnacle blennies, another dozen fire fish, so dragon faced pipefish, a pair of Joculator angels, a dozen assorted captive bred pseudochromis and the list goes on. We have 1 juvenile goldflake angel in the tank now, with a second growing up in the outdoor frag tank. Another few months are we will put the two of them together and hopefully have a new pair.
Dave B
i cant think
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Im intrigued on what others think of this, I personally overstock my tanks in other peoples eyes. In my eyes, I wouldn’t say it’s overstocked, I have the territory, food and swimming room for everyone. As soon as the territory is completely taken that’s when I think a tank is overstocked. You want enough territory for there to still be unclaimed areas for some fish. In my 4’ tank I have 19-20 fish. 10 of which are wrasses (so near enough half of them) and yes everyone is boisterous to similar species - my rabbits every so often have some issue with eachother but it’s not consistent enough to be true aggression.
I think a lot of people consider overstocking in terms of bioload. But that's entirely dependent on the dynamics of your system. Do you have a tightly controlled system with limited microfauna or a sprawling food chain that processes every bit of organics you toss in? Are your corals growing so fast they consume everything your fish poop out or are you starting up with new frags? Most importantly for your fish, are they all being fed plenty and have enough personal space?
You might be overstocked with 10 fish at one point in your build but perfectly fine with 10 at a later time. No rule of thumb in my opinion, just monitor your tank and adjust as needed.
You might be overstocked with 10 fish at one point in your build but perfectly fine with 10 at a later time. No rule of thumb in my opinion, just monitor your tank and adjust as needed.
Rob.In.AZ
Community Member
3 things that I think of with overcrowding.
Nutrient export - your tank/ filtration can't keep up with the nutrient input.
Stress/ aggression - so many fish that you start running into stress and aggression.
Both those seem to work themselves out, if you get me. Things die, then you've got less crowding. Not a great approach in my opinion.
The 3rd is mounting a metric ****ton of frags all right on top of each other. Should give them some room to grow out, and think about how they're going to look years down the road.
Nutrient export - your tank/ filtration can't keep up with the nutrient input.
Stress/ aggression - so many fish that you start running into stress and aggression.
Both those seem to work themselves out, if you get me. Things die, then you've got less crowding. Not a great approach in my opinion.
The 3rd is mounting a metric ****ton of frags all right on top of each other. Should give them some room to grow out, and think about how they're going to look years down the road.
alexanderthefishlover
Active Member
Then I’m overstocked beyond belief because I have a water box 25p and I have 2 clowns, 1 yellow tail damsel, a lemon damsel, 1 yellow watchman, 1 six line wrasse, 3 tailbots, a green emerald crab, cleaner skunk shrimp, and a few tiny blue hermits.
I’ve had 0 issues no diseases besides a misdiagnosed ich case which was actually just sand.
My fish are happy and never want to actually hide they don’t feel afraid. Only the watchman hides.
I have a lot of corals too and everything seems to be going well. The fish are obviously small right now and if they do get you big I will not hesitate to surrender them to my speciality saltwater store.
But as of now my nitrates hardly rise and are at .5 0 ammonia and 0 nitrite.
My specialty store and I mean they are excerpts not random PetSmart workers, told me the 1 inch per gallon doesn’t apply to saltwater as long as the bio filter can handle the bioload
I’ve had 0 issues no diseases besides a misdiagnosed ich case which was actually just sand.
My fish are happy and never want to actually hide they don’t feel afraid. Only the watchman hides.
I have a lot of corals too and everything seems to be going well. The fish are obviously small right now and if they do get you big I will not hesitate to surrender them to my speciality saltwater store.
But as of now my nitrates hardly rise and are at .5 0 ammonia and 0 nitrite.
My specialty store and I mean they are excerpts not random PetSmart workers, told me the 1 inch per gallon doesn’t apply to saltwater as long as the bio filter can handle the bioload
GARRIGA
2500 Club Member
Can't overstock a tank but you can overstock it's filtration system including ability to maintain enough oxygen and expel co2 along with nitrogen. Why doubling or quadrupling the filtration shouldn't hurt and in the wild many fish roam in tight schools to avoid predation. Safety in numbers genetically imprinted in most we keep in singles or small groups. Don't worry. They won't act like unmanned electric vehicles crashing into each other. 
Lets be honest. Who wouldn't want a tang gang tank
Lets be honest. Who wouldn't want a tang gang tank
Paul B
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My tank is over stocked. I probably have 45 fish but most of them are small and the tank is 125 gallons. Soon they will have to take turns sticking their heads in the water to breathe
Solo McReefer
Valuable Member
Can't overstock a tank but you can overstock it's filtration system including ability to maintain enough oxygen and expel co2 along with nitrogen. Why doubling or quadrupling the filtration shouldn't hurt and in the wild many fish roam in tight schools to avoid predation. Safety in numbers genetically imprinted in most we keep in singles or small groups. Don't worry. They won't act like unmanned electric vehicles crashing into each other.
Lets be honest. Who wouldn't want a tang gang tank
GARRIGA
2500 Club Member
Never said anything about size of life in that box
