20 gallon long and the little guppy that could

For tetras you should plan on at least 6 of each type but the more the better since they are shoaling fish and need others of their kind. With a 20 long I would go with just one or two shoals. I have 4 shoals neon, ember, glow light and red eye tetra in my 55 gallon tank. My biggest shoal is my glow light tetra (14)
So if I do one school of maybe 12 tetra with 5-6 Cories? For now I have the guppy in there too, though I may move him to my 55 with the other 2 guppies. Will that max out the tank? Maybe a couple honey Gouramis?
 
So if I do one school of maybe 12 tetra with 5-6 Cories? For now I have the guppy in there too, though I may move him to my 55 with the other 2 guppies. Will that max out the tank? Maybe a couple honey Gouramis?
I would do 12 tetras and 10 corydoras and that will max out the tank. It will be better for the corydoras to have a larger group
 
I've really been enjoying this tetra-related conversation. We have glowlights and neons, too (6 of each). We plan on getting another half dozen neons, a couple of nerite snails and a couple of prawns (64l tank, roughly 2' x 15" x 18". They're such cheerful little fish.

The glowlights had been in alone for over a month before we added the neons, but they seem to shoal with the neons and have gained confidence. (Or maybe it's because they've learned that at feeding time, if they hang back they'll get nothing because the neons will scoff the lot!)

Beautiful set up BTW, Viking. I imagine a tank that size with carefully managed fish stocks virtually runs itself if you are religious about your water quality. Your substrate looks very similar to ours (1/16th aquarium gravel), with gives me confidence.
 
Weekly water changes are a fair amount of work. My water is hard so I have to mix RO water in to soften it. Those 5 gallon jugs of RO water are heavy but I have a new supplier who charges only 29 cents a gallon which is 1/2 what I was paying. My neon and glow light tetra do seem to school together nicely. My embers tend to stay in my anarharis forest on the left side of the tank. My red eye tetra were fry that hid in the tank after I removed the red eye shoal and gave it to my bother-in-law. I started with 5 (2 f/3m) They kept having fry show up one or two at a time and in 3 months I had 17 red eyed tetra and they were starting to take over the tank. After I gave them away I found another small fry so I let him stay, then about 1 month later I found 3 more fry 2 didn't make it but 1 turned out to be another red eye. So I have 2 red eye tetras. I hope to have some neon or glow light fry show up. My ember tetras are my favorite because they are so small and at feeding time they bravely get right in there and compete. They also stick together in a nice group.
 
Be wary of assuming the filter will be instantly cycled. You should not have seen an ammonia spike in an established tank - even if you had dead fish in there.
I would err on the side of caution and treat it as a fishless cycle. If the filter is indeed cycled your initial dose of ammonia should be taken up within 24 hours and you will have 0 ammonia and 0 nitrite. You will only have lost one day. If you still have ammonia or nitrite after 24 hours let the cycle complete.
 
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Be wary of assuming the filter will be instantly cycled. You should not have seen an ammonia spike in an established tank - even if you had dead fish in there.
I would err on the side of caution and treat it as a fishless cycle. If the filter is indeed cycled your initial dose of ammonia should be taken up within 24 hours and you will have 0 ammonia and 0 nitrite. You will only have lost one day. If you still have ammonia or nitrite after 24 hours let the cycle complete.

Yes, thank you; I decided to be cautious and wait, just put in plants and let it all acclimate for a while before adding fish. My only local stores are PetSmart and Petco and I went out looking for plants today but they had very little and what they did have looked awful. Any recommendations on good online sources for aquatic plants that can survive in sand and that will work well for tetra? Not sure yet on cardinals vs neons; likewise will probably order online because I'm concerned about quality in the chain stores, particularly because with COVID they haven't had much turnover of their stock.
 
Be wary of assuming the filter will be instantly cycled. You should not have seen an ammonia spike in an established tank - even if you had dead fish in there.

Also - what can cause an ammonia spike in an established tank, other than wiping out the bacteria?
 
A
Also - what can cause an ammonia spike in an established tank, other than wiping out the bacteria?
dead fish, decomposing food and waste
 
Yes, thank you; I decided to be cautious and wait, just put in plants and let it all acclimate for a while before adding fish. My only local stores are PetSmart and Petco and I went out looking for plants today but they had very little and what they did have looked awful. Any recommendations on good online sources for aquatic plants that can survive in sand and that will work well for tetra? Not sure yet on cardinals vs neons; likewise will probably order online because I'm concerned about quality in the chain stores, particularly because with COVID they haven't had much turnover of their stock.
There's a lad on YouTube - George Farmer - who does aquascapes. He usually says which plants he's used and how easy they are to grow etc, and says where he got them from. His tanks are amazing! (He has fish in them, too, but his emphasis is on the plants) You could look at his videos for ideas.

Not sure if I'm allowed to "advertise" someone like this - apologies if I'm not
 
A

dead fish, decomposing food and waste
I must have somehow wiped out the bacteria, because unless that one dead fish that wasn't in there more than a handful of hours did it, I don't know what else did. I'm really pretty good at keeping up with cleaning.
 

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