if you post a pic of the other 2 gouramis we can id them for you
--------------------
Filters should be cleaned at least once a month (preferably every 2 weeks). Wash the filter materials in a bucket of tank water, then wash them in a second bucket of tank water. This gets most of the gunk out of the sponges and provides a cleaner filter. The filter case and pump (and any hoses) can be washed under tap water.
The gunk in the gravel and filters is fish poop and the less poop, the cleaner the water
--------------------
I would be doing a 75% water change each week due to the pleco. They produce a lot of waste, which rots in the gravel and can lead to problems. I'm not saying this is the problem with the male Betta but it could be a contributing factor. And keep gravel cleaning the tank each time you do a water change.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
With a big tank like yours, you could use a 2 litre plastic drink bottle (like a Coke bottle) as the gravel cleaner. Cut the bottom off the plastic bottle and remove the lid. Attach a length of garden hose (or clear hose) to the top of the bottle and run it out the door onto the lawn or garden. Then gravel clean away
--------------------
The Clown Loach, Corydoras, White Clouds & Scissortail Rasboras are all schooling fishes that prefer to be in groups of 10 or more. When the Betta issue is resolved, perhaps look at adding a few more to build their groups up.
Out of curiosity, how long did the Scissortail Rasboras live and what did they do when they died?
They should live for years and if you only had them for 18months or less, then something is not right.
--------------------
I would add frozen food to their diet each day to try and build them up physically. Feed dry or freeze dried food in the morning and then frozen or live in the afternoon/ evening. It doesn't have to be every day but more frozen or live food would benefit them.
Frozen but defrosted prawn/ shrimp, fish, squid, mussel, etc are good foods. With prawn, remove the shell, head and gut (thin black tube in body) and throw in the bin. Then use a pr of scissors to cut the prawn into small bits and offer a few bits at a time. Continue feeding until the fish are no longer interested. All your fish will eat prawn. The other foods simply get cut into small bits and offered the same way. Avoid the squid/ octopus beak (mouth) and remove the ink sac and quill, then cut the legs and body into little bits and feed to the fish.
If you have buckets of water outside under a tree, and they have leaves in, you might get mosquitoe larvae in them. Scoop them out with a fine mesh net, rinse under the tap and feed to the fish. Mozzie larvae are an excellent food for small aquarium fishes.
Aphids on roses or other plants can be tapped into a bucket and fed to the fish as well. As can any small flies or moths. Just make sure they are free of chemicals and pesticides. You can buy wingless fruit flies from universities and lab supply companies and culture them at home. They make a good food for fish.
You can culture Daphnia outdoors in small ponds. They feed on microscopic organisms that feed on rotting plant matter in the water. Same sort of places mozzie larvae frequent.
You can hatch brineshrimp eggs and feed the nauplii (baby brineshrimp) to the fish. The White Clouds and Rasboras will love them and the Bettas might eat them too. If you grow the nauplii up then the bigger fish will eat them too.
The pleco will need plant matter and driftwood in its diet. Do you have any driftwood in the tank?
You can feed slices of cucumber, zucchini, pumpkin or green leafy vegetables like spinach to most fish. Make sure it is free of chemicals and give it a good rinse with fresh water, then put some in the tank.
You can stick the food in boiling/ hot water for a few seconds before feeding to soften it up. This is more for the pumpkin, zucchini, etc.
If the other fishes eat this it is not a problem and will give them some vitamin C.
