Alternative stocking options for a 20-gallon tall aquarium

[paddyL]

Just set up three new aquariums - two 20-gallon tall ones and a ten-gallon. Got rid of some old ones that weren't doing what I wanted them to. The ten-gallon is for my vampire crabs, and I'm planning to put a giant betta in one of the 20s. Now I need to figure out what to do with the other 20-gallon. I'm looking for something a bit different - either cool behavior or an interesting look. It's gotta be bigger than your average small fish, but not so big it won't fit in a 20. I was thinking maybe an apistogramma pair - could be a species-only tank or a community. My pH is around 7, which works for a lot of fish. I can adjust it with Indian almond leaves or driftwood if needed, or use crushed coral to raise it.

Also thinking about tankmates for my giant betta - any ideas? Open to suggestions for either tank.

[sSjey]

GH is more important than pH when it comes to recommending fish for your tank. To give you better suggestions, could you please share the water hardness, specifically the GH, of your water? If you're on mains water, you should be able to find this information on your water provider's website - just make sure to note the unit of measurement. For those with well water, taking a sample to a local fish store for testing would be a good idea.

[paddyL]

My water parameters are pH 7, GH 25, and KH 20.

[boomer]

I'd love to clarify, what's the unit for your GH and KH numbers - are we looking at degrees (DGH) or perhaps ppm (mg/l)? It makes a huge difference, as 25 and 20 would be extremely hard if in DGH, but quite soft in ppm.

[paddyL]

Gh - 25mg/l. That's quite soft.

[boomer]

With very soft water, you'll have more options for fish, and the risk of acidic water is a plus. Assuming your 20g high tank is 24 inches long and 12 inches wide, you've got a good space for small-sized fish. Most will be shoaling, so a group of 10-12 would be ideal. These could work as dither fish for a pair of apistogramma, although personally, I'd want a tank with at least 30 inches of length – but let's see what the cichlid experts think. Soft sand substrate would be perfect for a group of pygmy cories. Floating plants are a must for almost any fish you choose. Since I'm not sure what you're into, it's tough to suggest specific fish, but as long as you stick with small species, you've got plenty of options.

[paddyL]

I've got a pretty standard 20 gallon tall setup planned - 24 inches long, 12 inches wide. The equipment and decor will likely include two sponge filters, one on either side, Carib Sea super natural sand for the substrate, and some live plants like Java fern, anubias, and pothos. I'll also add some giant duckweed for a floating plant layer, along with driftwood and dragon stone for decoration. A few small caves will provide some hiding spots for the fish. The water temperature will be around 79 degrees.

For stocking, I'm considering an Apistogramma cacatuoides pair. I've also thought about adding some clown killifish or marbled hatchetfish to the mix. However, I've heard that keeping mid to bottom dwelling fish with an apistogramma pair can be problematic, as the females tend to become quite aggressive during breeding.

[paddyL]

I'm also considering keeping just a single male apistogramma as the focal point, and then filling out the rest of the tank with some schooling fish.

[rockyfox]

I was also thinking about peacock gudgeons, they're pretty unique and have interesting behavior, and the males have that awesome coloration. They're small enough for a 20 gallon, and I think they could work well with some of the other fish I've been considering.

[boomer]

Just set up three new aquariums - two 20-gallon tall ones and a ten-gallon. Got rid of some old ones that weren't doing what I wanted them to. The ten-gallon is for my vampire crabs, and I'm planning to put a giant betta in one of the 20s. Now I need to figure out what to do with the other 20-gallon. I'm looking for something a bit different - either cool behavior or an interesting look. It's gotta be bigger than your average small fish, but not so big it won't fit in a 20. I was thinking maybe an apistogramma pair - could be a species-only tank or a community. My pH is around 7, which works for a lot of fish. I can adjust it with Indian almond leaves or driftwood if needed, or use crushed coral to raise it.

Also thinking about tankmates for my giant betta - any ideas? Open to suggestions for either tank.

If you're set on keeping a pair and want to raise fry, be aware that substrate fish will likely snack on them at night. Apistos can be quite territorial, and they won't take kindly to cories. I've had success keeping dwarf cichlids with cories in larger tanks, but it's a different story in smaller ones. My experience with Bolivian Rams is a case in point - they spawned four times, but the cories always managed to get to the eggs under the cover of darkness. It ended badly for the female Ram, too.

For Carnegiella strigata, I think a longer tank would be better suited, like a 30-inch 29g. However, they are calm swimmers, so it's not out of the question in a 20g. You'll want to provide more substantial floating plants with gaps in between, though. Duckweed isn't ideal - try Water Sprite, Frogbit, or Water Lettuce instead. You can thin out new or older plants to create the right balance of cover and open water. Carnegiella will mostly just hover in place, only moving when they're feeding or interacting.

By the way, 79F is a bit too warm for cories - they prefer it around 23-25C or 73-75F.