GSP Size and Growth

[Wyomingite]

Well, coupla questions 'bout GSP size. For years I've seen that GSPs reach 6". Kept quite a few over the years and have never had one reach more than 3.5" or so, even after 5 or more years. Most seem to stop growin' at 'bout 3". Honestly couldn't tell ya the longest I've ever had one, maybe 8 or 9 years. Most I've had to pass on to new owners at some point 'cuz of the dreaded move... anyways, I have some questions that I've never seen definitively answered in any journal article, book, or on-line source.

Is that 6" an average length or a max length? I've kept maybe a dozen or so oscars over the years. Seen the size for oscars listed anywhere from 15" to 18". Had one that reached 15.5", several max out at 14", have had a couple that maxed at 10", but overall IME the average seems to be between 12" and 13". I've seen the same trend in most of the cichlid species I've kept repeatedly over the years; a small percentage reach the size often listed in resources, but the average size is generally a bit smaller by the time ya figure in genetics, sexual variation, and (with species that have been bred long term in captivity) size reduction in captive-bred strains. I've found this to be consistent with the published literature on cichlids, but I've found studies of GSPs to be scarce, at least in the journals I regularly have access to. Is this the trend I'm seein' with GSPs, or am I doin' something wrong? Is everybody but me regularly raising their GSPs to 5" or 6"?

Do GSPs need full marine conditions to reach that full 6"? Never kept one in full strength marine water, generally buy 'em in FW and over a period of time acclimate them to high-end brackish with a specific gravity between 1.015 and 1.018. Stop there mainly because I've always had a brackish tank or two running with brackish species, but have only dabbled in SW a little bit years ago.

Am I just not keepin' them long enough? What kind of growth rate should I be seeing? Example, I've had my largest GSP right now for two years and he has gone from 1.5" to app. 3" TL. In that time I've had convict cichlids, my green terrors, three species of mbuna, and my Neolamprologus brichardi pair spawn numerous times and the fry of all but the most recent batches have exceeded him in size. Should he be larger than that?

He's in a 55 gallon with a sp. grav. of 1.012. 20% water change weekly, temperature runs at 78°. Nitrates are usually between 5-10. Plenty of rockwork. Tankmates are a knight goby and 2 other GSPs, each at 2". They get frozen shrimp once a week, frozen blood worms twice a week, and all the ramshorns and MTSs they can eat the other four days. That's all the puffers will eat. The knight goby grazes algae, as well, for what that's worth. Something missing in the diet has long been one of my main suspects for growth deficiency in my GSPs, but I've tried every trick I can think of to get them to eat other foods, without success. Any suggestions or observations would be appreciated.

So, here I am, ultimately THIS is what led me to join this forum. I'm a zoologist with a background in Wildlife Management, with practical experience with genetics and nutrition, though primarily in cervids. Been outta the profession for a few years, but that doesn't keep the practical knowledge from conveniently transferring to the hobby. I've been keeping brackish and FW fish for 29 years, I've been able to coerce over 100 species of fish to spawn and have raised the fry to adults. With every species I've kept repeatedly I've had individuals reach the max size or close to it, but never even close with these guys. My F8s and modestus are exactly where I'd expect them to be for the amount of time I've had them. I cannot raise GSPs above 3" or 3 1/2". The only thing that I know of that I have not tried is putting one in full strength marine water at 1.021 or higher. I find satisfaction in knowing that I've given my fish as healthy a life in my aquariums as they woulda had in the wild. As far as I can see, that's not happening here. I'm at wit's end. Any insight would be appreciated.

Cheers,

WYite

[CoCoPuffs]

Well, it's interesting to me that I've never seen a full grown gsp in a pet shop. Seen plenty of other extremely large aquarium fish, but not them....that says to me the conditions aren't right.

[RTR]

Well, coupla questions 'bout GSP size. For years I've seen that GSPs reach 6". Kept quite a few over the years and have never had one reach more than 3.5" or so, ...WYite

Your GSPs are stunted.

So are your Oscars, but less severely.

Very few tropical fish hobbyists ever see full-size captives because they do not really know much about what is required to keep fish in captivity and have them achieve full adult size, and/or live out their full captive lifespan. The standard aquarium practicesof mixed tanks and commercial hobby foods.especially coupled with too-small tanks and small and/or infrequent water changes does not do the job and never will.

If you want to keep puffers in captivity and have then full size (or larger), you have to follow different practices. That full size being the longest standard or total length* as recorded on Fishbase or other non-hobby reference site. Captive lifespans should be high multiples of natural average lifespans. The difference in lifespan is a function of the short lives of most fry in the wild. Remember that if one adult fish in the wild produces one, repeat one, offsping which lives to reproduce, that fish has held its place in the species gene pool. If it produces more than on offspring which in turn lives to reproduce, then it has increased its hold on the species gene pool.

*Standard Length = the measure from the front of the fish to the caudal peduncle.
Total Length = the measure from the front of the fish to the tip of the tail.
Science tends to use the standard length (S.L.), while the hobby may use total length (T.L.) more often, but may use either so long as which one is specified.

We can breed only a very few puffers in captivity, but effectively unlimited Oscars. Whether or not those are healthy fish and achieve max size and long lifespans depends on the care they are given. That care is not at all what most to pet shops suggest.

There are many articles here on the care and management of puffers in captivity on this site. due to technical issues, not all are available at the moment. Hopefully that will be corrected soon. In the meantime, some of the articles are available in a separate forum here, and there is plenty of expertise available among the more experienced members here. The care and feeding of puffers (or of large Cichlids) is rarely to never the same that the local fish stores or chains recommend.

IMHO & IME the first and most important requirement is space. Far larger tanks are absolutely required for puffers (and for large Cichlids) than are commonly suggested. Also those tanks must be better filtered and more frequently changed that is routinely suggested. Also the feeding is likely to be quite different, and the stocking basically limited to the target fish prinarily or only. Only when puffers are kept in excellent water quality in quite roomy tanks and pretty much on their owm (abslutely no tankmates in the same niche as they occupy) are you reasonably assured of full-sized fish - and that starts quite small fish sized and involves rapid growth prior to puberty. It is demanding in a way, but in practice is actually far easier than standard (pet store style) tank care.

Folks here can and will teach you how to grow all the puffers you want to full adult size. Breeding is yet to be conquered for most, but are still learning.

The choice is yours.

[Pufferpunk]

Both of mine grew from 2-6" in 2 years in a 55g, which turned out to be too small for the both of them.

[jus85411]

same, i had a GSP that within a few months shot from about 3-5". watch out for MTS, their shells are a bit too hard and puffers have been reported to break their "beaks" on their shells. pond snails are the most frequently used and are cheap if not free. just get a small tank together, feed some spinach and other veggies, you should have egg sacks and babies in no time!

i agree that the tank size was most likely the issue, at least with the mentioned ones(3 of them in a 55). most people suggest 40 for each GSP because of the size, bioload and messy eating habits. the smallest suggested is 30 for each, but bigger is always better since you take up water volume with decor and such.

my GSP when he passed from air being trapped in him, he was approx 3 1/2 - 4 years old and a "total length" of about 5 1/2 inches. just under 5 "standard length". another thing recommended by many here are vitamins to soak the food in while it defrosts. the most suggested for marine is "selcon gel", its a bit pricey but it will last a good bit. i always soaked my puffers food in this. you could also try a more varied diet. my puffers diet consisted of cubes of bloodworms, mussel, squid, mysis, and clam. he also regularly got fed half shell on littleneck clams(frozen to kill parasites, and thawed in tank water + selcon as well), market shrimp(again frozen etc like the clams), and i would get him a treat once in a while that was a live crab/crayfish. i also usually had ghost shrimp as a clean up crew that he would hunt over time and he nibbled at algae sheets that i had for my lawnmower blenny

[CoCoPuffs]

Well, it's interesting to me that I've never seen a full grown gsp in a pet shop. Seen plenty of other extremely large aquarium fish, but not them....that says to me the conditions aren't right.

Finally saw a full grown one today. Wouldn't say it was fist sized, but it was close to 6''. The guy who gave him away said he raised it full marine, it's whole life....

[sgtmyers88]

My GSP's have showed considerable signs of growth and they are looking very round with beautiful bright coloration! I would say they are 2.5 inches now!

I have noticed that one has started to look a bit stubbier and rounder with larger spots while the other has a longer and squarish face.
Species or Sexing Variation? (note the different tail colors as well)

[Pufferpunk]

I'll bet you $100 I look nothing like you!

[sgtmyers88]

I'll bet you $100 I look nothing like you!

haha ok

[RTR]

Do not bet against PP, you will lose!

Individual variation. GSPs are found quite widely in the wild, and they are quite variable fish to fish.

[Corvus]

I'd be very surprised if GSPs were only one species with no subspecies or regional variants with different maximum sizes (compare the works of Dekkers, who found at least three in different areas, which we now likely all would call GSPs).

I've seen both GSPs reaching 6" in a few years and others never reaching more than 3" with equal, very good water quality and tanks of sufficient size (e.g. in one case >> 90 gallons for 2 freshly imported specimens).

Generally bad water conditions as well as a lack of space also lead to smaller sizes. Therefore, in my opinion it's hard to tell if a GSP is truly stunted without knowing more about its history and the conditions it was kept in.