**Proposed MINIMUM recommendations for aquariums with multiple fish. These MINIMUMS do not work when only one LARGER fish is alone in the tank... in that case, use the "Tank Size Guideline" below:**Small Fish - 1 Gallon per adult size inch for fish up to 3 inches as adults. (This is the only type of fish that fits in the 1" per gallon rule. Fish that will be small even as adults.) (Also see Hailey's 10 Gallon Tank Stocking List And Suggestions )

Medium Fish - 2 Gallons per adult size inch for fish 3" to 6" as adults. Minimum Tank Size - 24" to 48" long (6X to 8X longer than longest expected adult sized fish in the tank)

Medium Large Fish (including most Fancy Goldfish) - 3 Gallons per adult size inch for fish 6" to 10" as adults. Minimum Tank Size - 48" to 80" long (6X to 8X longer than longest expected adult sized fish in the tank).

Large Fish (including Oscars, Common Pleco's, Comets and Common Goldfish) - 5 Gallons per adult size inch for fish over 10" as adults. Minimum Tank Size - 80" long and UP depending on expected adult size of fish using the basis of 8X longer than the longest expected adult sized fish in the tank.

**Koi should really be in a large pond since most aquariums are not large enough unless you have a HUGE tank.**

**NOTE - When measuring your fish, use their expected adult size, not the current size. Do NOT include the tail. Measure from the base of the tail, where it connects to the body or use the expected adult size found on reputable profiles and care sheets (see separate article on Profiles/Care Sheets). We are more concerned with body mass for figuring out bioload in a tank. Some fish like Angelfish, Discus, round-bodied Goldfish, etc., should probably have the length and width added together to come up with a more accurate comparison to long-bodied fish.**

(BELOW ADDED FOR BLOG THAT WAS NOT IN ORIGINAL THREAD)

One mathematical formula shows that larger fish grow by eight times in body mass for each time they double their length. So a 2" fish would be equal in body mass to eight 1" fish. A 4" fish would be equal in body mass to eight 2" fish or 64 1" fish. An 8" fish would be equal in body mass to eight 4" fish or hundreds of 1" fish. Another formula I saw that made it simpler stated that fish do not grow just one dimensional. They grow three dimensional so you should multiply their lenght by height by width (4"x4"x4"= 64", 2"x2"x2"=8", 1"x1"x1"= 1" so this simple math formula works for determining a simple body mass index). Here is a site that has an actual mathematical equation (oblate ellipsoid) for determining body mass on your fish... http://www.geocities.com/Tokyo/4468/weight.html

**TANK SIZE GUIDELINE:**

Also, your tank should be at least six times (6X) to eight times (8X) longer than your longest expected adult sized fish so it has a decent amount of space to swim before having to turn. For example, if your largest fish is going to be six inches as an adult and a slow swimmer, your tank should be at least 36" long. Most 36" long tanks are in the 30 - 60 Gallon range so this gives you a baseline also. A six inch fish based on the above rules would need around 18 gallons of water but if you only have one six inch fish, you would still need at least a 36" long tank. This means you would actually need a bigger tank than the minimum gallons due to its swimming needs. Your tank should also be at least 1.5X wider than the fish so it has room to turn at each end.

Another big thing for Goldfish is filtration and circulation. The general rule for filtration is 4-6 times your tank gallons for most tropical fish... but Goldfish and other large messy fish (Plecos, Oscars, etc.) need at least ten times (10X) filtration/circulation since they are messier than most other fish.

Here is a link to Aquarium dimensions, weights, etc., that I found for tanks up to 180G.

http://www.alysta.com/books/fishtank.htm

You can also check "standard" sizes for tanks, including BIG tanks by going to where I and many other aquarists have bought their tanks online.

Acrylic Dimensions - http://www.glasscages.com/?sAction=ViewCat&lCatID=41

Glass Dimensions - http://www.glasscages.com/?sAction=ViewCat&lCatID=2

(END OF ADDED INFO)

Below is the information edited for the above proposal of guidelines for beginners (formulated by me with some follow-up comments on another thread by other experienced fish keepers):

Topic: Working on "new" rules to replace the 1" per gallon rule

Many aquarist's have heard of the "1 inch per gallon rule" or "1 gallon per inch rule". Many LFS (Local Fish Stores) or LPS (Local Pet Stores) or CPS (Chain Pet Stores) advise new aquarist's of this rule. I know the PetsMart even gave me a copy from their manual which advised this as well. The problem lies in the fact that the "1 inch per gallon" rule only works for small fish that will be less than 3 inches as adults and the "1 inch per gallon" rule does NOT work at all for Goldfish or any other fish that are expected to grow to over 3" as healthy adults.

Please look over these proposed minimum "rules" and post your positive or negative comments here but mainly trying to actually add to the ultimate success of a better simple set of rules. I know these will never be perfect, as there is no perfect set of rules, but hopefully something SIMPLE yet better than the 1" per gallon rule can be developed.

These are my proposals based on my readings of many web pages, threads and the comments posted on the previous thread started by "LylaLandrum - This just occurred to me...".

Thanks in advance for your help.

GoldLenny

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**And now some select comments:**

By Mbuna4me:

There is no 1 inch of fish per gal of water rule, its more guideline.

By LylaLandrum:

mbuna--

Perhaps you didn't read the previous topic. Lenny here has put a link to it in case you are in the dark. We know there is no perfect set of rules. However many people don't understand the 1 inch per gallon rule and I’ve seen people with oscars in 20 gallon tanks saying it is ok and it is not. We are attempting to devise a BETTER set of guidelines because 1 inch per gallon is, well, stupid.

Lenny I did some basic research on your guidelines and the math all seems to be working out. I think that would be, not perfect, but would work for beginners.

My reply to LylaLandrum:

LylaLandrum,

You came up with this idea so you will get proper credit when I put the final proposal on a web page. I'm just trying to keep it going to see if we can get a general consensus that these proposed simple "guidelines" will be better than the 1" per gallon bad guideline that I and many others were misled with by the LFS.

Based on all of the circumstances that I found on the net and here in the forum, this simple set of "guidelines" seems to work. I'm sure there may be an exception, mainly when dealing with only single fish, for example, one 12" fish in a 60 Gallon tank? I don't know if the 60 G tank would be big enough for it but two 12" fish in a 120 Gallon tank would work out pretty good.

GoldLenny

By LylaLandrum:

Yes, those work well for single fish, and then lemme think, (again, I’m more of a frog than fish girl) one 14 inch fish needs 70 so I think the general rule for 2 14 inch fish was 30g per additional fish, so maybe on those guidelines we can tack on that those apply for one fish, if you want more than one of those fish divide the gallonage (is that a word) in half and that's what you need for the 2nd....or maybe that's too much for a beginner...I’m not sure, but it is something to think about, I think...or maybe something like 2 gallons per inch of adult fish after the largest fish, if that makes sense, LOL, but I’m sure this basic formula will work.

Reply by me:

Hi again Lyla,

I'm not a big fish guy yet so I wasn't sure on the Large fish guidelines.

From your last post, does that mean that a single 12" fish would be OK in a 60 G tank? I was thinking it would be a little small but I guess it depends of the dimensions of the tank. I read in the other thread that the tank should be 6 times longer than the fish so a 12" fish would need a 72" or 6' long tank. I don't think any 60 G tank that I've seen is that long. Most 60 G tanks are only 3' to 4' long. That's why I was thinking the large fish rule would only work with two fish or more so the "gallonage"(total volume) would be doubled.

Keep the ideas coming for the next revision to this "new" and BETTER set of guidelines.

GoldLenny

Comment by Rohnds:

I have seen many who have formulated various equation or formulas or rule to determine how much/many fish you could keep in an aquarium. These individuals have taken a non-scientific process and is trying to create a scientific formula with non-scientific tool. That is the irony. You simply cannot take the dimensions of the tank or volume (equate to gallons) and create a formula to determine how many small, medium or large size body fishes can fit in your aquarium. A simple rule or formula must stand vigorous test. You must be able to plug in data at from each end of the spectrum. Then if the rule/formula can withstand these data then it becomes a valid rule/formula. If even one set of data fails this rule/formula then the entire rule/formula becomes useless. For example many believe that the minimum "gallonage" required by an adult Oscar is around 55 gallons. If you were to place a single Oscars in a tank that is 2 inches high, 120 inches long and 60 inches wide, would it survive? Why not, you a total of 62 gallons? See what I mean by data at extreme end. In this case the rule is completely useless.

That is lot more to it that just these parameters. Here is number of other factors that determine the number of fish you could keep.

1. Volume of the tank i.e. # of gallons.

2. Dimensions of the tanks.

3. Surface area. This directly relate to amount of O2.

4. Type of filter. More directly that GPH rating of your filter.

5. Surface area of the filter media. Directly correlate to amount of beneficial bacteria.

6. Frequency of water change.

7. Amount of live plants. This again relate to amount of O2 in your water.

There are various other factors involved that contribute to the number of fish you could stock in your aquarium. These are the one I can think of right now.

Keep a non-scientific process non-scientific. Aquarium science is not a hard science and we should not treat it as such. The amount of research and data you need to collect in order to create even a simple rule/formula can be painstaking and time consuming. Believe me, I am telling you this from experience.

Rohn

My reply:

Hi Rohnds,

Thanks for your well thought out reply. I had written a long reply to your reply but when I went to Post, the forums servers went down like they've been doing a lot lately, so I'm just posting this short reply to say thanks. I'll post more later.

I think you do agree that the 1" per gallon rule or guideline only works for less than 25% of fish types or sizes which clearly is not a very good guideline.

Keep your ideas coming and once again, this is just supposed to be a SIMPLE set of guidelines to replace the obviously very flawed 1" per gallon guideline.

These guidelines do work for your example of an Oscar (12" to 16" as adults) which would mean 60 G to 80 G. Also, 99.9% of beginner aquarists will start off with some type of STANDARD tank so I don't think the extreme dimensions you posted would be applicable very often.

Once again, thanks for your contribution and please provide more exceptions. The more exceptions I get to test this SIMPLE formula, the better I can make my web page when I create it.

Well, the web page has been up for a couple of years and has had a few edits but generally speaking, the first "proposal" has worked out well for most fish keepers. So spread the word that the "One gallon per inch, FISH KILLING, rule" has been upgraded for the 21st Century.

Thanks,

GoldLenny

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You also want to be sure that your tank is wider than your fish is long. I haven't done the math to see if that would conflict with your rules any, but you don't want a 16" fish trying to turn around in a 12" deep tank.

ReplyDeleteHi Anonymous and thanks for visiting and for your reply.

ReplyDeleteI agree I do not directly address that "dimension" but unless someone is going with a custom built tank, it should not be a problem. A 16" fish would require at least 80G per the 5G per adult sized inch BUT would also require a tank 6X to 8X longer than it (depending on whether it's a slow or fast swimmer). Considering the length of the tank should be 96"(8') to 128"(10'8"), which are generally 180G++ sized tanks and the shortest side dimension on those "standard sized" tanks would be 18" according to http://www.alysta.com/books/fishtank.htm AND/OR http://www.glasscages.com/?sAction=ViewCat&lCatID=41 OR http://www.glasscages.com/?sAction=ViewCat&lCatID=2, then the guidelines are still working.

Keep the inquiries coming though. The more questions that I can check this "guideline" against, the better other visitors can be assured of it working for them.

Once again, thanks for visiting and posing new questions.

GoldLenny

http://malawicichlids.com/mw01019.htm

ReplyDeleteThanks for the MalawiCichlids webpage but while I fully understand what that page is saying, the majority of new fish keepers will look at that for about 10 seconds and say, "HUH???".

ReplyDeleteThat's why I started this page... for a decent but simple set of rules, as I have in bold larger letters above, also copied here...

"Proposed MINIMUM recommendations for aquariums with multiple fish. These MINIMUMS do not work when only one LARGER fish is alone in the tank... in that case, use the "Tank Size Guideline" below:

Small Fish - 1 Gallon per adult size inch for fish up to 3 inches as adults. (This is the only type of fish that fits in the 1" per gallon rule. Fish that will be small even as adults.)

Medium Fish - 2 Gallons per adult size inch for fish 3" to 6" as adults. Minimum Tank Size - 24" to 48" long (6X to 8X longer than longest expected adult sized fish in the tank)

Medium Large Fish (including Most Fancy Goldfish) - 3 Gallons per adult size inch for fish 6" to 10" as adults. Minimum Tank Size - 48" to 80" long (6X to 8X longer than longest expected adult sized fish in the tank).

Large Fish (including Oscars, Common Pleco's, Comets and Koi) - 5 Gallons per adult size inch for fish over 10" as adults. Minimum Tank Size - 80" long and UP depending on expected adult size of fish using the basis of 8X longer than the longest expected adult sized fish in the tank."

GoldLenny