Stocking Help (20 Gallons)

[RainyDays]

My tank is 20 gallons, currently set at 26C. I'd like some advice on some stocking plans, as well as your opinions on whether these fish are compatible with one another and with a 20 gallon long tank.

Currently, I have:
2 guppies
5 rummynose tetra (upping to 8)
6 cardinal tetra (upping to 10)
4 peppered corys (may up to 6)

I looked online before hand and read that 26C would be a good temperature for these fish, however I've also heard that the peppered corys are not temperature compatible? Should I be rehoming these and swapping them for, say, bronze cories?

Finally, I would like some advice on centrepiece fish! One type that has caught my eye is the Opaline Gourami, however there seems to be conflicting information on what minimum tank size is suitable for them (usually it seems to be between a 20g minimum or a 35g minimum). What are your opinions on this?

Thank you!

 

[Byron]

It is important to know your water parameters other than temperature (which can be adjusted obviously), namely hardness (general or total hardness, GH) and pH, and carbonate hardness (KH or Alkalinity). These if you do not know them you may be able to find on the website of your municipal water authority. So far you have mainly soft water fish except for the guppies which need moderately hard water, but we need to know the numbers to sensibly suggest fish.

On the temperature question, most cory species are better with lower temperatures than high, and by lower I mean in the range of 21-24/25 C (low to mid 70's F). A few species manage in warmer water. Corydoras sterbai is one that does. Both the bronze (C. aeneus) and peppered (C. paleatus) are temperate species. But this can work; I keep my 50 or so wild caught cories at 24 to 24.5 C (75-76 F). And my rummynose are in the same tank, and my cardinals are in a tank with this same temperature. Except for a very few species, it seems better to be more temperate in temperature. A degree or two may not seem like much, but when temperature is what drives a fish's metabolism, this is important. So with the fish you now have, lowering the temp to 24-25 C will be fine.

As for "centerpiece" fish, this is not easy to achieve in smaller tanks. A 20g long will best suite smaller shoaling fish, like those you have (except the guppies). I agree wiith increasing the numbers, but I wold do it in reverse...rummynose tetra is one species that is always better with more. A 20g is limited space, but increasing this group to 10 will make quite a difference to the fish, and provide more interest as they are more active. The cardinals could be increased to 8.

The Opaline Gourami is not something you want in this tank. This species, Trichopodus trichopterus, has several varieties (man-made through selective breeding), such as Blue, Gold, Three-Spot, Marble, Cosby and Opaline, so behaviours are those of the species, and this is one of the most aggressive of the small-medium sized gourami. There are smaller species that might work, but I'd like to know your parameters first as they can be more demanding.

Byron.

 

[NickAu]

If you want some interesting fish you might consider a Betta sorority.

 

[RainyDays]

Byron-

Thank you very much for your help! My testing kit says that these are the levels:
GH - 300ppm
KH - 180ppm (Falls in the Slightly Hard section on the chart)
pH - 7.4

I will follow your advice then on the temperature and lower it to 24.

Staying clear of the Opaline Gourami sounds best then! My very first stocking plan had involved having a Dwarf Gourami, however I went off this idea when I heard there may be problems with it and the guppy. Would any other species of gourami be okay?

I see, then I'll swap the rummynose and cardinal numbers around!

Another fish I had thought of was German Blue Rams. Would one of these be suitable with gourami, or would that overstock my tank?


NickAu-

While it's something I'd love to do, I already have some fish in my tank, though perhaps in the future!

 

[Souperman]

Something to research into if you still want a gourami is the honey gournami. It is one of the most peaceful dwarf gourami. I have one in a community tank and I have never had any problems with it.

 

[Byron]

GH - 300ppm
KH - 180ppm (Falls in the Slightly Hard section on the chart)
pH - 7.4

Are these test results for your source water (tap water, on its own), or the aquarium? I'm asking because these are high, and that means very hard water, which is not going to work for the tetras (or many cories). If different, what is the GH of your tap water alone?

Staying clear of the Opaline Gourami sounds best then! My very first stocking plan had involved having a Dwarf Gourami, however I went off this idea when I heard there may be problems with it and the guppy. Would any other species of gourami be okay?

Let's get the GH pinned down first. But aside from that, the Honey could work. And the Dwarf is a risk for disease, true.

Another fish I had thought of was German Blue Rams. Would one of these be suitable with gourami, or would that overstock my tank?

Generally, cichlids and gourami should not be combined because they are so similar in temperament (males are territorial, etc). Here you do not have space for more than one of whichever (again, water parameters may affect this). But another issue with rams is temperature, they must have it warm, 80F (27 C) which could work for the cardinals and rummys but not most cories as earlier set out.

 

[RainyDays]

Byron-

These are the results of my Aquarium, however they were tested using test strips about 5 weeks ago, so I'll be testing them again soon with a better tester. I'll test them again with the strips when I get back.

I may go with a honey gourami then, unless you can think of anything else that will work? Thank you!

 

[Byron]

Byron-

These are the results of my Aquarium, however they were tested using test strips about 5 weeks ago, so I'll be testing them again soon with a better tester. I'll test them again with the strips when I get back.

I may go with a honey gourami then, unless you can think of anything else that will work? Thank you!

Test strips have various reliability, so you might consider a liquid test like the API Master Combo; it has pH, ammonia, nitrite and nitrate. Normally you do not need to be testing GH and KH because these values in the tap water tend to remain fairly stable with regular partial water changes. However, that depends upon what they are to start with, and if they are being targeted by something in the aquarium. I cannot offer much on this until I know the GH and pH of the tap water on its own. Test the tank water too, and report any differences.

This is very important. The fish mentioned are all soft water species, and if the water really is as hard as 300 ppm (over 16 dGH) this is a significant issue.

 

[RainyDays]

Byron-

Will do! My main reason for buying the test strips was the LFS being out of the API Master test kit.

After looking online at my supplier's website, they simply list the water as being "Slightly hard" with a pH of 7.67. I will try contacting them to find a more accurate figure.

EDIT:
It lists Slightly Hard as being 101-150mg/l. It seems the test strips are incredibly unreliable.

 

[Byron]

Byron-

Will do! My main reason for buying the test strips was the LFS being out of the API Master test kit.

After looking online at my supplier's website, they simply list the water as being "Slightly hard" with a pH of 7.67. I will try contacting them to find a more accurate figure.

EDIT:
It lists Slightly Hard as being 101-150mg/l. It seems the test strips are incredibly unreliable.

Here's another example of why we ask for numbers and not rely on subjective terms. Assuming the 101-150 mg/l [which by the way is the same as ppm, parts per million] is correct, I would term that soft to moderately soft unless it is at the 150 end in which case it is just moderately hard. This makes a significant difference to the suitable fish species, so if this again is accurate, you're generally OK there.

I must still stress though that we need you to test the tank water to see if the GH is the same, or very close; the pH will likely be different from tap to tank, but it is the GH we need to be certain about. We may find that the GH is the same or different, and if you get the same result (whether or not accurate) testing tank water and tap water, we should be OK to assume they are the same, and then go with the lower number as more accurate. Does this make sense?

Byron.

 

[RainyDays]

Byron-

It does thank you! Tomorrow is water change day, so I'll retest the aquarium water and my tap water, and let you know the results.

 

[RainyDays]

The results are:

Tap water-
GH - 140ppm
KH - 45ppm
pH - 7.6

Aquarium-
GH - 135ppm
KH - 100ppm
pH - 7.6

No idea why the KH jumped, though the test strips were likely unreliable.

 

[Byron]

The results are:

Tap water-
GH - 140ppm
KH - 45ppm
pH - 7.6

Aquarium-
GH - 135ppm
KH - 100ppm
pH - 7.6

No idea why the KH jumped, though the test strips were likely unreliable.

Yes, that is odd...but we can I think assume fairly confidently that the parameters that really count are the same, so we know what you are working with now. The GH is around 7-8 dGH, so that is not bad.