What dictates stocking limit for a FOWLR?

[Ben jammin]

I am curious how you determine what an appropriate fish load is for a FOWLR tank. I have a 270 with a mix of some larger and some smaller fish. I only feed the large ones (angels, puffer, cowfish, wrasses etc), and the small ones (yellowtail damsels, royal gramma, various sand sifting gobies) basically serve as my water column and sandbed cleanup crew, eating all the small pieces of food that the big guys ignore and would sit on the sanbed uneaten. So since the smaller fish actually serve that purpose, and occupy a different habitat in the aquarium, it seems to me that they don't really add to the bioload of the tank and just counting fish, or even inches of fish, is not a good measure.

So what is the right measure? Can you add any number of fish gradually as long as you keep compatibility in mind and can keep nitrates at a reasonable level? Or is there some other factor that dictates how much is too much?

 

[jedimasterben]

Bioload is measured only by the amount of food you put into the system, how many fish, what they eat, etc is irrelevant.

Just don't import significantly more than your nutrient export. Look into an algae scrubber if nitrate levels become an issue (either for fish health reasons or algae).

 

[eatbreakfast]

Nutrients in the water and aggression between the inhabitants. If you can keep your nitrates in acceptable levels rhen there is no real limit to quantity of fish.

 

[Bad Company]

I am aware of five limiting factors to fish stocking:
1. Oxygen replenishment (a function of surface area for gas exchange, agitation, bubbles etc)
2. Waste breakdown capacity, Ammonia through Nitrate export (a function of your overall filtration with respect to food input as mentioned above)
3. Fish swimming room requirments (a function of the species behavior and tank size)
4. Fish needs for territory. Some fish are accusomed to have a set amount (a function of tank size and fish mentality)
5. Fish compatibility. This is often self correcting and expensive :]

 

[reeffirstaid]

There aren't stocking rules, there is common sense. Every species has individual needs and requirements. You must research species, find a few that are able to exist with a similar set of requirements, and won't bother each other. If your aquarium can supply them with adequate water space, up and until they reach their maximum size, then you have your stocking list. Stocking lists are the product of research, understanding and patience. Given your tank size and mix, angels, puffers, cowfish - you probably have enough large fish to fill the tank, once each species reaches adulthood.

 

[Ben jammin]

Thanks for the responses. The bioload being a function of food put into the system, rather than # of fish, makes sense. In my situation, I am currently feeding 2 cubes of food and about a nickel to quarter size quantity of frozen krill twice daily. This is in a 270 gallon tank. It feels like a lot to me - how does that compare to the amount that others feed their fully stocked tanks of similar size?

I've seen lots of photos and videos of people with 200-300 gallon tanks with many more fully grown fish in them than I was planning on having. As Jeremy mentioned, stocking has to be done slowly and carefully, but that also means I have to have an idea of the number of fish I'll be able to add so I can decide which ones I want and when. I definitely would like to add a picasso trigger and powder blue tang, for example, but I know both can be very aggressive. I'm considering adding a blue jaw trigger and maybe a blonde naso as well, but I'd want to add those before the picasso and powder blue since they are less aggressive. I wouldn't want to add those at all though if they meant no picasso or PBT, so I need to have a sense of whether I'll have the carrying capacity for all those fish when they are fully grown. Thus, it's not good enough to say just add one fish at a time and see how things go.

 

[DrBoxedWine]

***Full Disclosure*** I do not have a saltwater tank, yet. So bear in mind this is advice is based off of my freshwater experience.

I have 2 African Cichlid tanks, where overstocking is the name of the game. I've noticed that you can "just tell" when you're tank is overstocked. The fish store i went to originally sold me a bunch of juvies that were all fine in my 75g, but as they got bigger (about 1.5 years later) it was clear I had too many large fish in the tank. They just seemed stressed out, not as mellow as they used to be, some of the fish were too active for the others (especially considering how small the tank was) and they weren't displaying their natural behaviors like they used to (they like to sift through the sand, and they weren't doing it as much anymore). I find fish tanks to be relaxing and peaceful, and seeing the fish clearly stressed out took a lot of the enjoyment out of watching the tank. I ended up getting a 125g and moved all the big fish to that tank. It's clearly a better home for them, they're more relaxed and display natural behaviors again. All this being said, I know people who pack in way more fish than I do and think the mayhem is just fine. I'm not sure if i'm right, or they are. I think the key is tinkering around and finding what works for you, and just keep in mind the end size of the fish. I'm guessing getting a fish out of a SW tank is a bigger PITA than my cichlid tanks, but things aren't permanent... Do your best to get it right, but rehoming sometime down the road isn't the end of the world. Reading as much as you can and getting as much info on each fish and compatibility is very important, but it also comes down to the individual fish and your unique setup...

That was all about aggression and compatibility, obviously keeping your nitrates and nutrients in check is something that is more cut and dry. If you can't keep them down, then something needs to be done.

 

[vlangel]

I used to service tanks that size for customers and they of course wanted as many fish as possible. I always told them to keep in mind that if they stocked their tanks to its maximum capacity that they were diminishing their margin for disaster. Let's say there is a prolonged power outage, will the fish rapidly use up their oxygen or foul their water. When you are in the service business you see all sorts of disasters and I personally would allow my tank some wiggle room if I had a large tank.

 

[Ben jammin]

Interesting perspectives. Good points you raise vlangel. Out of curiosity, in your experience servicing tanks in the 250-300 gallon range, how many cubes a day of food was generally put into what you would consider a healthy system?

 

[vlangel]

I am assuming you mean the frozen cubes? I suggested to my customers no more than 4-5. One of my customers had 19 fish in her 240g DT. A lot of her fish were big too and while she was on vacation we had storms and everyone's power in the area went out. I knew her fish were at risk so I went to her house at 7am but couldn't get in cause the keypad needed electricity. I called a friend of hers and had them bring a key. She arrived 8ish and in the 8-10hrs the electric was off 11 of her fish died. She bought an automatic generator after that and still keeps 2 battery back up pumps on the tank as a precaution. She also keeps her fish load smaller now 14-15.

 

[Ben jammin]

Thanks vlangel. That sucks about your customer. I actually have a service that installed my tank (had it built into the wall when I built my house) and they have been telling me I am okay on capacity, but I always like to get lots of perspectives and then draw my own conclusions. I have 20 fish in the tank now but 11 of those are small (<2") damsels or gobies that I don't account for when feeding (they clean up the scraps) and won't get any bigger. Three others are in the 3-4" range and won't get much bigger (flame angel, yellow tang, dwarf lion (too small to eat the damsels)). The fish I have that will eventually get large include a longhorn cowfish, spiny box puffer, french angel, red coris wrasse, dragon wrasse and naso tang. So that's six. All are 4.5" or smaller now so it will take them some time to grow. I've got a 6.75" harlequin tusk coming tomorrow and as stated above, would like to add a majestic angel, powder blue tang, quinquevittatum wrasse, and picasso trigger. My service says I'd still have room for one or two more like a blue throat trigger and maybe a blonde naso, but that's what I'm weighing now. I'd want to add those fish before the more aggressive ones.

 

[vlangel]

Yes, she was devastated. Her and her husband have names for their fish and they love them. That happened 6-8 years ago and she still has nearly all the same fish that survived and the new ones she added. She has a majestic angel, or a regal angel, (I can't remember) that is probably 7" in diameter. Its a magnificent fish.
On a side note, one thing I learned from my service job is if the tank is experiencing any type of lack of oxygen for any reason, tangs will be the first to experience distress and angels are next. Clownfish, damsels, cardinals and puffers will be the last to succumb.

 

[Ben jammin]

One thing that story tells me is I need to go out and buy some air pumps for if I ever lose power.

I can relate to your customer. We name all our fish and my son and especially daughter love them like pets. Our aussie tusk came this morning and I think he is already my daughter's favorite and we haven't even turned the lights on yet. He's a beautiful fish though. We've already named him - Raymond, which probably seems like an odd name for a tusk (or any) fish except to those who watch House of Cards. :wink:

 

[vlangel]

One thing that story tells me is I need to go out and buy some air pumps for if I ever lose power.

I can relate to your customer. We name all our fish and my son and especially daughter love them like pets. Our aussie tusk came this morning and I think he is already my daughter's favorite and we haven't even turned the lights on yet. He's a beautiful fish though. We've already named him - Raymond, which probably seems like an odd name for a tusk (or any) fish except to those who watch House of Cards. :wink:

I have a battery back up pump on my own tank that has a cord plugged into an outlet and only kicks on when it detects loss of power. They only costs about $15. After that one incident I put one on every single tank I serviced. We didn't lose any more fish to power failures after that.

 

[Ben jammin]

Where did you get that kind of a kit that only turns on when power loss is detected? And are you using it on just an airpump, or a circulation pump? I don't have any circulation pumps in my tank as I get enough flow from the returns.

 

[vlangel]

Where did you get that kind of a kit that only turns on when power loss is detected? And are you using it on just an airpump, or a circulation pump? I don't have any circulation pumps in my tank as I get enough flow from the returns.

The pump comes that way, but it is only for aeration, (with airline tubing and airstone). It has a cord to plug in the outlet and I guess it works like your clock radio when it goes to battery back up in a power outage.