Reddit mentions of Penn Plax Aquarium Heater Fully Submersible Within 1 Degree of Accuracy 50 Watt Heats Up to 10 Gallon Tank

The aqueon 50w adjustable is great (as others have suggested) but I have this one at 7in tall: Penn Plax Aquarium Heater Fully Submersible Within 1 Degree of Accuracy 50 Watt Heats Up to 10 Gallon Tank https://www.amazon.com/dp/B000VOF33Y/ref=cm_sw_r_cp_api_i_j-C0DbC1T387E

I would suggest just going crazy on your filtration and getting an Aquaclear 50. It's suitable for 20-50 gallon tanks and you can put a whole lot more media in there. I have an AC 20 on my mother's 5.5 gallon betta tank and that works very well, barely any current at all and neons can deal with currents very well and the shrimp won't care.

I would return the filter and get an adjustable one off amazon for the same or less. There is a 20 gallon, 100 watt heater on amazon for $11.80 with prime, so I would go for that. Had them in my tanks and I haven't had one break or malfunction in the year and a half I've had them. Great deal!

15W for lights, might be a little low for plants in a 20 gallon, so get beginner level plants.

Important: research fishless cycling in an aquarium. This is how you will have the most success in the aquarium world. Better for your fish and better for your sanity when you put the fish in. It will get that nitrogen cycle pumping at 100%, so it will be ready for all the junk from your fist few fish.

As far as substrate, I have heard of black diamond blasting sand and this is what it looks like in an aquarium. I believe I have it in mine. It's very cheap, but is very dirty so when you get it, you'll have to rinse the dust out of it. It will take several rinses. Do this in a rubbermaid or a 5 gallon bucket (get them at lowes or home depot. If you want to get some marble for rock piles, lowes sells broken product and will throw in a bucket for free usually). DO NOT rinse it in your tank, it may scratch your glass. 98% of aquarium substrate needs to be rinsed, just throw about 3/4 or a full gallon in a 5 gallon bucket and swish it around. This black diamond stuff sometimes has little glass things in it, so use a glove or a stick (I used a well-washed spatula) and tap water.

You won't need to gravel vac in a properly cycled, planted aquarium. Trust me, especially with that filter, you won't need to, and that's a blessing. The beginner plants will grow under almost any light, and root tabs are a must for sand, especially in new aquariums. It depends what kind of gravel, but plants will usually take hold. I like sand because the poop either gets trapped where I can't see it or gets circulated to the filter.

I believe that's marbled(?) pothos. It works really well for sucking out the nitrates. I have a clipping clipped on the edge of my other tank, and it's working VERY well like that, so you could clip one on the edge of your tank next to your filter cutout. They do have different water roots than soil roots, so just get a cutting of viney part and make sure some of it is wet and there you go. Ferts also help these guys, and all I use is flourish excel and comprehensive, but you don't need to get into all that quite yet.

personally, I love the snails, they clean up my overfeeding, which leads to bad algae problems, my buddy killed all of his and got bad algae so I always have snails in my tanks.

As far as shrimp, they won't overpopulate when pressured by the tetras. they will eat the babies and the bolder ones will pester the adults a bit, so they won't breed as often. If your tank gets overrun (which it won't), you could try and sell them back to the store for store credit, or you could sell online.

Plants and shrimp: aquabid.com It's pretty much the ebay of the fish keeping world. notice that if it doesn't say snail free, you may get hitchhikers, which are not necessarily bad things. It takes maybe 24 hours to get an account (because of wait) so apply tonight.

DO NOT buy a feeder fish to 'jump start' your tank. It's inhumane and will take the exact same time (probably longer now that I think about it) as fishless cycling with ammonia would. You REALLY need to research that. Basic premise is, raise ammonia to 3ppm, monitor it every night, when you see it drop, bring it back up. Then when it disappears in ~3 days, check your nitrites, get them back to readable levels via water changes, then add ammonia, watch nitrates drop, and when you can get from 3ppm ammonia to 0ppm ammonia and 0 ppm nitrites, in 24 hours, then you can add a few fish. This is where you need a liquid test kit, not a test kit with strips, they can be unreliable.

this is a good source about fishless cycling. I haven't used dr. Tim's and my buddy got frustrated and crashed his tiny tank (after using Dr. Tim's, buddy's fault, not tim's) when he first started, so I have no idea how it works. I have just used ammonia both times I've cycled a tank.

Wait until you have a nice home for your fish before you shove them in there. You would want to wait until your home has A/C, a roof, walls, and is free of asbestos before you move in, right? Same with fish, be nice to them and you'll have a whole lot less headaches when it comes to ammonia spikes and stuff like that.

I'll just add a bit more to azul's post, since s/he was so thorough. :)

Ideal temperature is 78-80F, which many preset heaters have a hard time managing. You can probably find an inexpensive adjustable heater online (like this one, preset to 76F but adjustable; my thermometer reads 80 and the heater is set at 82).

Eheim heaters tend to be ENORMOUS even at smaller wattages, so depending on how much space you can stand for it to take up, there are smaller options! Eheim is probably the best as far as quality, though.

I see you purchased a tank kit, so good for you! I was going to recommend the updated Fluval Spec V, a bit pricey but all the components necessary (except a heater!).

If you're interested in doing plants, r/plantedtank is great for that! Please be cautious when buying plastic plants as they will most often rip fins. Silk or live plants are best for bettas.

I'm less than helpful with saving sick fish, unfortunately, but there are many folks here who are a wealth of knowledge if you have more questions! Good luck to you and your new little guy. I know you will give him your best! :)

Naruto mostly, maybe the Switch cover (don't have one but it's a planned future purchase)

I'm thinking that $25~ would be fair for a pre-seeded corner sponge filter (looks like this one), a Marina internal power filter plus four new cartridge refills, and a heater

how would you recommend going about that?

do you think something like this would be too much for a 5 gallon?

https://www.amazon.com/dp/B000VOF33Y/_encoding=UTF8?coliid=IY8TMX4AJBEQ1&colid=2I9V6ILP1GAOH&th=1

would my goldfish be ok with increase in temperature? how high would I increase it and at what rate?