Not sure on the filter.
What are your stats in ammonia,nitrite,nitrate,and ph.
Is the fish in the 75gal.
How many fish and which type.
Where is the fungus on the fish and does it look fluffy.
Use both the melafix and pimafix together.
You can buy an airpump and add an airstone.
I don't know the stats wilder (funds low, long story) The fish in the tank are
2 Lace Gourami
2 danios (1 dead I believe but cannot find it)
1 Rendahls catfish
2 platies
1 apisto blue head
2 clown barbs
1 Bristlenose
The fungus is white and fluffy on the clown barbs but also fin's rotting and tail one of the platies is on the gravel unwell the apisto will not make it. I moved my 2 angelfish and kribensis out to my 32 gallon as they had 0 signs of being unwell other than lethargy the kribensis is not well still however my angels are good. The fungus has hit the platies danios barbs and a little on the gourami's.
Take water samples to the lfs and tell them to write the readings down for you.
Try the melafix and pimafix, but if its a bad strain it might not clear it up.
when you take the water samples to the lfs try and pick a stronger bacterial med up.
Good luck.
well I am going to the LFS today and was thinking of getting Pimafix. It has killed off a ram and 2 SFF's already. Whats the best Medication for Fungal and bacterial that won't ruin the filter ect and is safe with scaless and catfish.