A Beginner's 20g Long Aquarium (Platys + Pygmy Corys)

Hi, I'm a relatively new member here, but you might have seen me already. I first took an interest in fish tanks this fall, and for my birthday in October my dad's coworker gave me their used 20 gallon. It's been up and running for about 3 months now, and I feel like it's really coming together! I really enjoy researching the science and biology behind fish-keeping.
The tank:
Current Stocking:
3 Painted platys (Julian, Susan, and Gertrude)
3 Zebra danios
2 White cloud mountain minnows
10 Neocaridina shrimp (5 cherry and 5 rili, of varying sizes)
~4 Pygmy corydoras
2 Otocinclus
2 Ramshorn snails (+like a bazillion babies)

Water Parameters:
temp: 75 degrees
hardness: 8 dH, 6? dKH (150ppm; somewhere between 120-180ppm)
pH: 7.5

History:
Started cycling toward the end of October, added live plants (2 gold ribbon and an amazon sword) as well as 4 zebra danios to provide ammonia. Completed the cycle in a few weeks with no issues. Added duckweed, java moss, crypts, a cool stick, 8 neocaridina shrimp (6 cherry/2 rili), 2 rams horns, and 2 WCMMs (something of an impulse purchase, kinda regret it as they need colder water than everything else). Unfortunately lost 4 of my cherry shrimp to the hang-on-back filter before I figured out where they were going and acquired a pre-filter sponge. Also lost 1 danio around this time to unknown cause. Added a cave made of a few rocks, and removed most of the duckweed. Snails had babies. Added 3 platies abt new years. Lost 3 of the remaining shrimp to unknown causes, but whatever it was subsided because the remaining one has done fine. Rescaped the tank a week or two ago to have a more 3-dimensional hardscape, and introduce more plants.

This past Wednesday, I bought 6 pygmy corys, 2 otos, and brought the shrimp back up to 10. Had a debacle over the past few days making sure the otos had enough food, but I've gotten them to eat Repashy Soilent Green, and also borrowed a slimy piece of driftwood to feed the otos for a while and introduce more algae to the rest of the tank.

Unfortunately one cory was very small and stressed when I bought it, and one more is MIA, but I hope to buy a few more once things settle down and I have the feeding situation figured out.

I'm planning to rehome the danios and white clouds on Monday, since they are very greedy eaters and make the cories/otos nervous. I'd like to replace them with some emerald dwarf rasboras eventually.



P.S shoutout to my dad, who used to own a large LFS and now runs the local Petsmart. He's had lots of great advice for me and I think he enjoys me following in his footsteps. I think he was actually active on this forum back in ancient times.

@AdoraBelle Dearheart @Seisage

That's a great tank. I really like the hardscape. It should be fun to watch it develop plant-wise. You've got a good eye for things.

I'm glad your otos seem to be doing okay so far! It's very good news that they ate the repashy. Hopefully they continue to do well.

The tank looks really nice. I'll always love the way a 20 long looks. Long and shallow is the best tank shape, in my opinion. Is that large branch the wood you're borrowing? I think I remember you saying in your other thread that you think it's too big and doesn't work for your tank, but I think it actually looks really nice in there.

May The Force of The Hobby Be With You!!

We have more in common than you realise - my parents were also in the aviaries and aquatics business for decades, owned their business, but had long retired by the time I got into keeping fish myself. In fact, it was helping to maintain my dad's ancient and last remaining tank as he was now in his 80s and couldn't manage the maintenance on his 57g living room tank anymore, so I learned more about fish in order to help care for his tank, and wound up taking it over really, and he said he wanted to give it to me for my own use once I'd started getting tanks of my own, and I've now inherited it after my dad passed in 2023.

It's lovely that you can have that bonding and passing on of wisdom from generation to generation.

It's been clear from your other thread, how hard you worked to save those otos (and are doing really well with them, which isn't easy! So you deserve kudos for that), and the fact you're so keen to learn and do the best for your fish, and enjoy your tank, is wonderful, and exactly the kind of person we want in the hobby and on the forum!

Sounds as though you've been doing pretty well getting the tank set up the way you want it. I agree with @Seisage that a 20g long is the perfect size tank, for a starter tank, for aquascaping, for many types of fish... footprint of the tank counts a lot more than volume of water for many fish, since they swim horizontally, not vertically! So tall tanks, or tiny tanks labelled as "starter tanks" are often much harder to maintain good water quality, and can't stock many types of fish, compared to a tank like a 20g Long.

Your early problems with shrimp etc are common when a tank is newly set up. Shrimp are especially sensitive to any fluctuations in water conditions and parameters, and in the early days of setting up a tank, fluctuations are common as it takes 3-6 months for a tank to really become fully established, and the hobbyist get into a regular routine of water changes to manage the bioload of the tank, and plants settle in and get established. These early issues are super common, you're not the first or last to make mistakes, and you worked really hard to correct them, that's the main thing! There isn't a person in the hobby who hasn't made a mistake.

I'm loving the look of the tank, but of course, once the otos are in much better condition (and they were in poor condition when you got them, not because of you, and it might be the same with the pygmies you lost. It's hard to pick healthy stock when you're new to the hobby), then you can always rescape it the way you want. Tropica has a some amazing aquascapes ranging from easy to difficult if you ever want inspiration! They've even got a section called "inspiration" where I've spent many hours. You can not only see the photos of the scapes, and the lists of the plants used, but in most you can delve deeper and see how they created the structure of the susbtrate and hardscape that they built the rest on.
Excited to follow this journal and watch your journey! Happy to see that you intend to remain on the forum and participate, I'm sure you could also enter this tank into a tank of the month contest if you wanted to, right, @Fishmanic?

JackGulley said:

P.S shoutout to my dad, who used to own a large LFS and now runs the local Petsmart. He's had lots of great advice for me and I think he enjoys me following in his footsteps. I think he was actually active on this forum back in ancient times.

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He'd also be very welcome to join in again! People do return after long breaks some times, and more active members joining in helps all of us, so would be delighted to see you both participate!

@JackGulley
That is an awesome looking tank. Our April TOTM contest will be for 17 to 30 gallon tanks. We'd love to see you enter your tank in the contest.

Seisage said:

Is that large branch the wood you're borrowing? I think I remember you saying in your other thread that you think it's too big and doesn't work for your tank, but I think it actually looks really nice in there.

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No, that one is part of my own aquascape, and I too really like it
I used a picture from before I added the driftwood; this is what the tank looks like at the moment

I just kinda threw it in

Fishmanic said:

@JackGulley
That is an awesome looking tank. Our April TOTM contest will be for 17 to 30 gallon tanks. We'd love to see you enter your tank in the contest.

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I'm glad there's one coming up soon! I've been lurking here for a while and was disappointed that I joined a little too late to contribute to December's totm.

Fish photoshoot!



I really enjoy how one of the female platies (Susan) has more of a yellow color compared to normal painted platies. I almost wonder if she has a little bit of sunburst or bumblebee in her; I would be interested to see if I could eventually try to selectively breed for that trait. I think the bumblebee platies look really cool; if I find one in a store I might just add it and have 4 platies.

JackGulley said:

No, that one is part of my own aquascape, and I too really like it
I used a picture from before I added the driftwood; this is what the tank looks like at the moment
View attachment 335731
I just kinda threw it in

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Ah. Yes, the second piece of driftwood is not so pretty as it is, lol! Although could be worked into a scape... I prefer the branch you chose as part of your scape. But it does look as though it might have biofilm that the otos might be feeding on. Where have you seen them spending time?

Otherwise, I do love the look of the tank! It's impressive, especially for a first tank!

A couple of things that could really help - some floating plants. Most fish appreciate the overhead cover, makes them feel safer from predators (they don't know there aren't any!) and floating plants are great for sucking up ammonia and improving water quality. Duckweed is awful, avoid at all costs - but amazon frogbit, red root floaters, salvinia, water lettuce -any of the larger floating plants are brilliant, and the fish will appreciate them, and fish that feel safer tend to come out into the open more.

A black background on the tank would also really make the plants and fish colours pop! As well as making them feel more secure, since the tank is very open right now. Doesn't have to be fancy, black construction paper will work, and is a cheap way to test it out and see if you like it!

After writing the above, I see one of the otos is on the added driftwood! They both look pretty good in these pics, and the platies and shrimp are lovely.

If you want to breed platies for certain traits, @emeraldking is an actual livebearer expert breeder, and knows more about livebearers than I know altogether about anything! He's your man for any livebearer questions.

Speaking of breeding, the other female (Gertrude) is pregnant! I've noticed she's a little bit rounder than the others for about a week, and today I noticed a prominent gravid spot. I'm a little bit confused tho, because judging by her shape (rounder but not square at all) and how long I've noticed it, I would expect her to only be recently pregnant. But today she had a dilated cloaca, and the male was harassing her a little bit, which I've read are signs of imminent birth? Although to be fair the male wasn't waiting to eat babies; he was trying to mate

JackGulley said:

Speaking of breeding, the other female (Gertrude) is pregnant! I've noticed she's a little bit rounder than the others for about a week, and today I noticed a prominent gravid spot. I'm a little bit confused tho, because judging by her shape (rounder but not square at all) and how long I've noticed it, I would expect her to only be recently pregnant. But today she had a dilated cloaca, and the male was harassing her a little bit, which I've read are signs of imminent birth? Although to be fair the male wasn't waiting to eat babies; he was trying to mate

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It can be really hard to predict when they're going to drop fry, even when experienced. They also often arrive in your tank already gravid from the store or suppliers, so it's not at all unusual for a female to arrive in someone's tank then pop out fry a few days later! Your dad will be able to tell you that.

If it's her first batch of fry, she's likely to have a smaller first couple of batches.

The male will continue to chase the females regardless, just because it's what male livebearers do

AdoraBelle Dearheart said:

Ah. Yes, the second piece of driftwood is not so pretty as it is, lol! Although could be worked into a scape... I prefer the branch you chose as part of your scape. But it does look as though it might have biofilm that the otos might be feeding on. Where have you seen them spending time?

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Yes, the otos love the driftwood! As do the platies, both pecking at it and exploring it. I don't like this piece (And I think I have to give it back; its from the Petsmart crab tank courtesy of dad lol), but I might try to work in a smaller piece when I rework the back right side, which is something I mean to do.

AdoraBelle Dearheart said:

Otherwise, I do love the look of the tank! It's impressive, especially for a first tank!

A couple of things that could really help - some floating plants. Most fish appreciate the overhead cover, makes them feel safer from predators (they don't know there aren't any!) and floating plants are great for sucking up ammonia and improving water quality. Duckweed is awful, avoid at all costs - but amazon frogbit, red root floaters, salvinia, water lettuce -any of the larger floating plants are brilliant, and the fish will appreciate them, and fish that feel safer tend to come out into the open more.

Click to expand...

I had some duckweed earlier, but it started making a mess when it got blown around by the filter so I purged it. There are still a few baby bits of it... I would like to look into more pleasant floating plants.

AdoraBelle Dearheart said:

A black background on the tank would also really make the plants and fish colours pop! As well as making them feel more secure, since the tank is very open right now. Doesn't have to be fancy, black construction paper will work, and is a cheap way to test it out and see if you like it!

Click to expand...

I do mean to have a black background, but I dropped my construction paper in the water last time I did a water change and I haven't replaced it yet

JackGulley said:

I had some duckweed earlier, but it started making a mess when it got blown around by the filter so I purged it. There are still a few baby bits of it... I would like to look into more pleasant floating plants.

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Yep, it's one of the reasons it's either loved or loathed in the hobby. I'm on the loathe side because it does make that mess, and also because once you have it, it's almost impossible to get rid of.

It reproduces fast, and a single leaf can quickly get out of control. If you spot any, get it out, immediately! Check under tank rim, the filter, any equipment etc, because it seems like even one dried out lead stuck on a net or something can rehydrate and then start another duckweed infestation.

I once soaked some equipment in a bucket of bleach solution outside, got distracted and left it for a few days, came back and found duckweed growing and thriving even in a bleach solution. It's a nightmare to get rid of. So if you don't want it, you have to be diligent in removing every trace of it that you find! Trust me on that one!