What Rule to use when stocking?

[Nasabeau]

2 Gallons per inch, 2 inches per 10 gallons, Per species requirements, doing research on how many fish I can put in a tank in my tank has shown me that there doesn't seem to be a consensus online on how to determine if your tank is overstocked. Right now I have a 75 gallon tank stocked with a coral beauty angelfish, a yellow tail blue damsel, a royal gramma, a pair of clownfish, and 8 assorted snails and 1 scarlet hermit crab. I have a canister filter rated for up to 100 gallons and a reef octopus classic 90 HOB skimmer. My parameters are stable right now, 40lbs of rock and live sand for the substrate. how do I know how many more fish is too many? what are your rules of thumb when stocking. I have learned so much about the fish I have, and what they can and can't go with, but I can't seem to find a straight answer on when to stop adding fish. In my fresh water tank I always used inch of adult fish for 1.5 gallons, but I get the sense that would probably be massively overstocked in the marine tank, given how active and territorial all these fish are. I was thinking of adding at least a handful more fish, or maybe just a couple of larger fish, and definitely adding some CUCs but I am not sure how to know when enough is enough, and I know without some guidance I'll end up overshooting it, because I want them all! XD

 

[Spare time]

I judge it by how well are the fish currently getting along with one another, can the fish escape and be away from the others, and if the current waste export method has enough capacity before needing to be adjusting significantly.


In my 75, I have a yelllow damsel, two clarkii clowns, a wantanabei angel, a lawnmower blenny, a diamond goby, and a melanarus wrasse. This is right where I am wanting to be, but others pack more.

 

[Nasabeau]

I judge it by how well are the fish currently getting along with one another, can the fish escape and be away from the others, and if the current waste export method has enough capacity before needing to be adjusting significantly.

right now they're all getting along swimmingly. the gramma has made himself two little caves to hang out in, the damsel and clowns have their little territories and the CBA doesn't notice any of the others. I am worried about using the method of "when they stop getting along that's too many" though because that means I would have to overstock the aquarium to find out its overstocked

Edit: when setting up my tank, I saw a guide that said "the more places your fish have to hide the less they will" so there are literally dozens of little hidey places for my fish and so far the advice was right, they rarely are hiding.

 

[laverda]

The only real rule is to research and know the animals you buying, including how big they will get and there needs.
Personally I would not add much more with the filtration you have currently. Canister filters are a recipe for hair algae growth. They work great at removing stuff worm the water column, but it is still in your system. All that crud breaks down to phosphate and nitrates. Unless you clean it at least weekly your going to have increasing nutrients until you have a algae break out. Ideally you want to rinse the filters and media in old saltwater once a week or or every 5 days.

 

[Nasabeau]

The only real rule is to research and know the animals you buying, including how big they will get and there needs.
Personally I would not add much more with the filtration you have currently. Canister filters are a recipe for hair algae growth. They work great at removing stuff worm the water column, but it is still in your system. All that crud breaks down to phosphate and nitrates. Unless you clean it at least weekly your going to have increasing nutrients until you have a algae break out. Ideally you want to rinse the filters and media in old saltwater once a week or or every 5 days.

I am rinsing the media every week on Saturday coupled with a 25% water change every other Saturday. I also have phosphate and nitrate sponges in the canister, my phosphate is a little up right now because of some of the food I was previously using, but those tend to stay low right now. also, this may make me kind of weird, but I've made it through the diatom bloom, I see it getting smaller every day, but I kind of liked the look of the cyano. weird question, is there any reason hair algae is bad for the aquarium? I know most people don't like it because they think it looks bad, but if its managed with like the CBA and maybe throw in a bristle tooth tang and some more crabs so it doesn't grow out of control, is there any reason that's bad for the fish? I think it looks kind of neat.

 

[xxkenny90xx]

Inch per gallon rules are old and outdated imo...

Ok go on your computer and print out actual size adult pictures of each fish you own and each fish you want. Tape them to your tank. How does it look? Too crowded? No? That's what I would do.

Also of course add fish one and a time and watch nutrients to make sure your filtration can handle it.

 

[Nasabeau]

Inch per gallon rules are old and outdated imo...

Ok go on your computer and print out actual size adult pictures of each fish you own and each fish you want. Tape them to your tank. How does it look? Too crowded? No? That's what I would do.

Also of course add fish one and a time and watch nutrients to make sure your filtration can handle it.

that's actually a really good idea, thank you! right now I'm adding a new fish every other week and watching params to make sure it stays stable after the new fish. I do plan on adding pairs at the same time, but so far that's been just the clowns and they were first in. I will definitely print out adult sizes and see how that looks!

 

[laverda]

GHA will kill your corals by smothering them. It can easily take over your tank.

 

[Nasabeau]

GHA will kill your corals by smothering them. It can easily take over your tank.

yeah, I started another thread about this actually, and it seems to be a common sentiment that they can take over the tank if you aren't careful. I will say I plan on having more anemone than coral, I just like the look of anemones more.

Edit, I guess I should clarify, I am terrified of hurting or killing corals or anemones by putting them in before I'm completely stable, so right now its fish only.

 

[Nasabeau]

Inch per gallon rules are old and outdated imo...

Ok go on your computer and print out actual size adult pictures of each fish you own and each fish you want. Tape them to your tank. How does it look? Too crowded? No? That's what I would do.

Also of course add fish one and a time and watch nutrients to make sure your filtration can handle it.

Thank you a lot for the advice. I printed out the adult sizes of the fish I have and the one fish I'm considering adding next. definitely don't think the tank will be overcrowded but actually seeing the sizes in real life gave me a great perspective on it. It's gonna be a lot fuller than I thought already. not too full, I just didn't expect it to already be as full as it will be if that makes sense.

edit, in case you are wondering, I am considering adding a flame fin tang. I figure if I add him young him and the CBA are more likely to stake out territories and generally leave each other alone, but if you have input there I am always open for advice

 

[PatW]

There are rules of thumb but they have problems.

There are fish with special dietary requirements. They require eating of live food like pods and that nearly constantly. So in that case, maybe just one and you hope your other fish do not clean out the pods.

There are very aggressive fish and some of these punch well above their “weight”. I scuba dive. Sharks are pretty shy and they are hard to get close enough to for a good photo. I have been attacked but only by pesky damselfish. I would think some of the more aggressive damsels could clean out an entire tank.

And there are guilds of fish. There are sand sifting fish, there are grazing fish, there are fish that hang out at specific territories and there are fish that swim in the mid water column. Fish with similar habits often compete in an aquarium. Fish with very different habits can be functionally invisible to each other.

And then there is the “INCH“ thing. I have a tang and it is just about 20% longer than one of my wrasses. But the tang is about 5 times the weight of the wrasse, is hyper active and eats and poops a bunch. One tang or 4 or 5 other fish.

 

[Nasabeau]

There are rules of thumb but they have problems.

There are fish with special dietary requirements. They require eating of live food like pods and that nearly constantly. So in that case, maybe just one and you hope your other fish do not clean out the pods.

There are very aggressive fish and some of these punch well above their “weight”. I scuba dive. Sharks are pretty shy and they are hard to get close enough to for a good photo. I have been attacked but only by pesky damselfish. I would think some of the more aggressive damsels could clean out an entire tank.

And there are guilds of fish. There are sand sifting fish, there are grazing fish, there are fish that hang out at specific territories and there are fish that swim in the mid water column. Fish with similar habits often compete in an aquarium. Fish with very different habits can be functionally invisible to each other.

And then there is the “INCH“ thing. I have a tang and it is just about 20% longer than one of my wrasses. But the tang is about 5 times the weight of the wrasse, is hyper active and eats and poops a bunch. One tang or 4 or 5 other fish.

I will say I am doing enough research on each fish to avoid ones where special husbandry is required because I don't know that I would have enough time to give them the care they need, so specialty diet fish are out. I already have two species of damsel (clown and YTBD) so I am not looking to tempt fate and add more damsels. right now I am leaning towards adding a tang to my tank (tomini tang) and MAYBE 1-2 chromis or the like, but was worried maybe my tank was already overstocked as is, because some of the inch rules would indicate that I am WAY overstocked (total inches of fish right now is ~18 inches (YTBD 2.75, 2x clowns 3, CBA 4, RG 3.5 off the top of my head), if you use 10 gallons per inch, I can have 7.5 inches of fish... logically it doesn't seem right but that is why I was asking what others do)

 

[xxkenny90xx]

Thank you a lot for the advice. I printed out the adult sizes of the fish I have and the one fish I'm considering adding next. definitely don't think the tank will be overcrowded but actually seeing the sizes in real life gave me a great perspective on it. It's gonna be a lot fuller than I thought already. not too full, I just didn't expect it to already be as full as it will be if that makes sense.

edit, in case you are wondering, I am considering adding a flame fin tang. I figure if I add him young him and the CBA are more likely to stake out territories and generally leave each other alone, but if you have input there I am always open for advice

I can't take the credit, I learned that trick from orionN

 

[Cole.mormon]

Per species requirement

 

[Nasabeau]

Per species requirement

see, my problem with using that for stocking is it doesn't really make sense. yes, obviously, each fish needs at least x number of gallons of swimming room, but they don't need that room exclusively, but they do need a smaller amount exclusively. for example, a clownfish needs at least a 20 gallons to be happy, but does that mean a 60 gallon tank is at max capacity with 3 clownfish? obviously not, since many people will keep clownfish pairs along with other fish in a 20 gallon. at the same time, you can't say "well it's more than 20 gallons, so it can hold clownfish" and put 30 clownfish in there. there is some in between here that tells when a tank is going to be at capacity. that's what I'm looking for. each species in my tank has to be happy with the room in my tank, yes, but they also have to not feel overcrowded in that space, and there is no reason to believe if I put a fish into my 75 that has a species minimum of a 75 gallon tank that no other fish can be in said tank.

 

[Cole.mormon]

No it depends. On each fish per species requirement. Aggression Max length l. Compatibility it all depends

 

[laverda]

Your think is correct. There is no hard and fast rule. Two fish that are fine in separate 30 gallon tanks, may not be fine together in a 300 gallon. One example would be two female maroon clowns. One will kill the other almost guaranteed.
The best we can do is learn the behavior of each fish we keep and try to provide that for them.

 

[Cole.mormon]

What @laverda said

 

[Nasabeau]

No it depends. On each fish per species requirement. Aggression Max length l. Compatibility it all depends

I guess my post was more about filtration capacity and overcrowding. obviously, per species compatibility, monitoring aggression levels, and each fish needs at least enough room for their species, but I'm confused on when to call it quits on adding fish. for example, my tank right now, 75g 4 foot, and I've got a tomini tang, a royal gramma, 2 ocillaris clowns, a yellow tail blue damsel, and a coral beauty angelfish. none of them show any aggression, the 75g meets each of their individual per species requirements, and my nitrogen cycle is running very well. How do I know if I can add more fish or not? do I just keep adding until aggression starts? I would think that's not a good idea, and quite frankly, the way I have it set up I imagine that would start long before I saw too high a nitrogen burden on the tank, since my nitrogen filtering capacity is something like twice what I need for a tank this size (at least based on vague and probably skewed metrics, either way, the tank will probably be able to support the nitrogen load of significantly more fish than I could put in the tank before the angel or the tang are going to go on a killing spree). this is why I really liked Kenny's answer, because it really gave me perspective on how big these guys are going to get, and from looking at it, it seems like a pretty good way to get a rough gauge on these guys. obviously, aggression can spring up with any two fish, and the best we can do is try and get a gauge based on species, but overall, I think just saying "per species requirements" is a really vague and just generally not great answer to stocking guidelines in a reef tank. because at this point, I still don't even know what you mean by that. do you mean, as long as the tank is above the minimum species requirement you can add it? or do you mean each fish needs the space minimum for it's species?

 

[Nasabeau]

Your think is correct. There is no hard and fast rule. Two fish that are fine in separate 30 gallon tanks, may not be fine together in a 300 gallon. One example would be two female maroon clowns. One will kill the other almost guaranteed.
The best we can do is learn the behavior of each fish we keep and try to provide that for them.

I get behaviourally, you can't keep certain fish together, and there is always the risk of aggression in any fish, but I guess my question is more about minimizing that risk in fish even when species compatibility is already taken into account. for example, I have a bonded pair of ocellaris clowns, which are generally considered peaceful fish, but I know even in tanks where all the species are compatible, too little space just for the clowns can make them become aggressive. I guess maybe this mentality that there has to be some way to know when to stop adding fish is based on my background in freshwater where filtration capacity plays a much bigger roll in your stocking (in my tanks before, the minute I went even slightly overstocked you'd see ammonia creep up, I get the sense that's not as common in reef tanks, since I see most people keep what I would probably consider overstocked tanks, judging by looking at fish per unit space XD)