Will different cory species school together? Plus some stocking questions

Hi! I have two questions, one about cories and the other about stocking with the cories. I have a 20 gallon planted tank with a male betta and six male guppies currently. I would like to add a school of 6 cories to the tank. I know for sure that I would like JuliI cories (most likely False juliis since they will be coming from petsmart), but my store usually only has 4 at a time. I am wondering if different species, such as peppered and juliis, will school together or if I need to keep 6 of the same species.

I am also wondering if it would be possible to add 3 more male guppies after I add the cories or if I would be way overstocking the tank. I have a good maintenance schedule and the tank will be heavily planted when I'm done with it so I'm fine with being a little overstocked, but I don't want to go too overboard.

I am including a pic of the tank and some detailed info below. Any advice is appreciated!

20 gal high
40 gal rated internal filter w/ ceramic filter media and sponges
100 W Hydor Theo Heater
pH: 7-7.5 buffered
Temp: 75-82 F
Black medium grain sand
Lava Rock & Driftwood
1 Male Betta
6 Male Guppies

 

Hi, different species of cories will interact with eachother but they will not school/shoal with eachother. Also I think a 20 high is a bit small for any cory that isn't a pygmy cory as they are very active and like their floor space.

 

Given that you got a betta, temps are a problem with many cories. Even the false juliis can only go max 78 which is borderline for both the betta (whose lowest should be 78) and the cories. Not ideal to keep at extreme ends of their ranges.

If you are set on cories, id opt for corydoras hastatus, corydoras sterbai, or corydoras aeneus (bronze or albino) as any of these can take the higher temperatures bettas need.

Peppered cories need below 77F. Cooler is better for them. So theyre not compatible at all.

6 of the same is best, as most prefer their own kind.

 

Depends on the cory.
In my big cory tank sterbs will blob up with anyone. If there is a group of cories swimming around sterbs will join.
Equis refused to associate with other cories. They also never blobbed up. Now in species only breeder.
Lasers preferred their own. Now in species only breeder.
Concolors are social and would join sterb blobs.
Duplicarious are occasionally social with other cories but generally preferred to hide and not blob on their own.
Longipinnis prefer their own and love blobbing up.
Supers seem indifferent to other cories as well as to other supers, though they are much happier in the big tank. In the species only 20 gal breeding tank they all stayed in a pile (Seriously, a pile. at one point it was 3 corries high) in the front left corner so I put them in the big tank. No blobbing up just happy independent rooting around in the sand.

 

Hi, different species of cories will interact with eachother but they will not school/shoal with eachother. Also I think a 20 high is a bit small for any cory that isn't a pygmy cory as they are very active and like their floor space.

Okay, I will go with all the same species then. That's something I am concerned about but I think I'm going to try it and see how they do. I will probably be getting a 20 long next semester so I can always move them in there too.

Given that you got a betta, temps are a problem with many cories. Even the false juliis can only go max 78 which is borderline for both the betta (whose lowest should be 78) and the cories. Not ideal to keep at extreme ends of their ranges.

If you are set on cories, id opt for corydoras hastatus, corydoras sterbai, or corydoras aeneus (bronze or albino) as any of these can take the higher temperatures bettas need.

Peppered cories need below 77F. Cooler is better for them. So theyre not compatible at all.

6 of the same is best, as most prefer their own kind.

My heater is set to 78 F so that is what the tank is for the most part. I have no problem setting it lower too since I have kept many bettas at 75 F in the past and they have all done fine. I live pretty close to Easy Aquariums in Gorham ME so I will see if they have any Sterbais or if they can get any in. If not I will most likely go with the Juliis.

Would adding three more guppies to this tank with the cories be too much?