Cory Tankmates For A 75Gal Tank

[Baccus]

Have you considered rainbow fish? Some of the rainbow species can get quite big are active and colourful they also wont bother the corys and should ignore your snails.
I am not sure what species of Rainbow fish will be available to you but you could also consider large school of Threadfin rainbows, Pacific Blue eyes or the much smaller Spotted Blue eye. Dwarf Neon Rainbows are another spectacular fish.
One of my big local Rainbow fish

 

[BaylorPerez]

i could go for those

 

[Byron]

They are a nice group of fish, the rainbows.  Just check the water parameter requirements, as some are fine in soft water (your GH of 4 dGH is soft), whereas some (the Boesemani for one) will not do well but need more mineral (higher GH).
 
Byron.

 

[Baccus]

To give you some ideas on suitable rainbows I have found this site very helpful
http/rainbowfish.angfaqld.org.au/Melano.htm
 
Many of the species listed probably wont be available overseas but I am sure some of the more common ones can be found with some searching.

 

[BaylorPerez]

So as my mother she wants me to get a rainbow shark. but i dont excatly think thats a good idea

 

[Byron]

So as my mother she wants me to get a rainbow shark. but i dont excatly think thats a good idea

 
No it is not a good idea.  Individual fish within this species can have different temperaments, but the norm is for this species to be very territorial.  Other substrate fish (I believe corys are being considered?) are not likely to work with a shark, whatever species.  And certainly no loaches, or fish of the several families.

 

[DoubleDutch]

Keyholes will be great for this tank. Very friendly fish that can be kept in groups (even more males). The C.julii are very likely C.trilineatus btw.

 

[Ridasha]

If you wish to stay within south American species I would very much recommend either angelfish or discus or silver dollars.  I  have 8 silver dollars in my 125G planted with 15 bronze corys and 20 neon tetras. Also angelfish in a 92G planted with 14 corys.  Very well behaved for the most part.  My silver dollars prefer meat over veggie when offered both at the same time so your plants might be ok if well fed. I also have a planted 37 with 6 corys but am trying to decide on centerpiece fish.  My planted 56 with tiger barbs and serpae tetras has no corys for obvious reasons.  Its too bad though, corys should be considered a prerequisite for any tank but they also limit on tank mates.  Might be a fluke but my two year old angel bit the tail clean off one cory  Definitely stressed it out to say the least.  Whatever you decide there is never going to be a perfect addition.
 
PS.  As mentioned sharks make one of the worst tank mates and are far to often acquired.
 
New member first post (keeping fish since 2004)

 

[DoubleDutch]

Trilineatus have other tempneeds than discus !!

 

[Ridasha]

Sure they do but they can meet in the middle of the ranges.  Never mind.    cheers !!

 

[Byron]

Sure they do but they can meet in the middle of the ranges.  Never mind.    cheers !!

 
This is not actually true, depending.  And certainly not true here.
 
First, one must understand that the water temperature affects fish very significantly, far more than air temperature affects most land animals.  The fish's internal processes and metabolism are primarily driven by temperature, and this can affect their lifespan.  The warmer the temperature, the higher the rate of metabolism, and the cooler the lower.
 
Second, the "range" of temperature is only a guide.  The lower and higher ends are not temperatures at which the specific species should be maintained permanently, but only guides as to what they should be able to tolerate for the short term, such as during summer heat waves.  In most cases, the middle of the range is where they will function best.
 
Temperatures in tropical waters do not fluctuate as much as some believe.  There is a diurnal fluctuation in many cases, but it is only a very few degrees.  And even with this, fish are able to swim into deeper and cooler water at will.  Maintaining a fish in the relatively confined space of the aquarium where the temperature is much more uniform is a very different thing.
 
Taking discus...these absolutely must be maintained in warm water, and most of the discus authorities will give 82F/28C as the absolute minimum.  There are only a few species of Corydoras that will be healthy at such high temperatures.  The range for C. trilineatus is 50-77F/16-25C, and as I mentioned above, the fish will be better closer to the middle rather than the upper limit.  So discus and this cory species would not work at all.  There is usually no "middle ground," unless the species have ranges that overlap significantly.
 
Byron.

 

[BaylorPerez]

for keyholes, are they mated pairs like angelfish?