raising live black worms for saltwater fish

Fish Think Pink

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Sorry for the ramble... I'll come back and clean this up when I have more time... 
Long story short, copper banded butterfly fish that ate thawed spirulina mysis at LFS before purchase, ate 3 in acclimation and then refused all food for weeks... finally about fourth week trying various thawed frozen foods started eating live black worms (took couple days trying 2x day every day)
Would get worms from Eastern Aquatics in PA (yeah, CA black worms from PA overnight to TX) and refrigerate
Fast forward to now, CBB still only eats live black worms (or dead once done wiggling in saltwater) but since all other fish think black worms are delicious, and even though I first make fish eat thawed variety other foods, every fish eats black worms (except lawnmower blenny who is only eating algae but developing pot belly... but figure give him more time... ). I'm going thru pound of black worms monthly. I moved from refrigeration box which given quantity of worms Eastern Aquatics says should be spread over cat litter box sized area of fridge (whole shelf?!!! family would FREAK). Went to my original QT plastic 3 or so gallon bowfront plastic tank (hate it for fish, distorts view of fish and think fish sees itself weird inside it too) that was sitting unused. 
NOTE: I have bare bottom basic plastic tank for worms. Any nitrification bacteria is built up on sides, bottom of tank. There is no filtration. When water looks discolored or foamy top, I dump it and give them new RO/DI. If I let water get tan (dirtier) then seem to free float so I need to strain the water so I don't lose dozen or so that may be free floating (I'm cheap, and I'm able to repurpose my fridge keeper middle section as strainer - photo below.)
I fill tank with about 3" or so of RO/DI water, have airstone. For months fed fish just Ocean Nutrition Formula Two Flakes (I have tangs - put veggie flakes in worms, put worms in herbivore fish)... If humans 'are what we eat' the internet popular feed brown paper towels sounded like <bleep> and never tried/did. Instead, gave flakes. Went thru entire jar of flakes. Did notice when it was time to restock worms because I go through them faster than they reproduce, old worms felt thinner than newly arrived worms (try not to mix old and new worms to cut down on bacteria contamination potential - like to clean up tank between worm batches. Around Thanksgiving 2021 noticed unused box of generic instant mashed potatoes in pantry someone bought and forgot. Internet or someone somewhere had also said worms ate instant mashed potatoes, so added some to flake food feeding worms both. 
Instant mashed potatoes and live black worms go well together! Have not yet done whole test yet, but worms definitely fatter and reproduction/yields DEFINITELY increased but not yet sure by how much. First batch I just randomly began adding instant mashed potatoes. Second batch I bought 2 oz of worms from local DFW worm person in case their worms have different internal beneficial bacteria which can help my fish become even more healthy, so can't accurately estimate how much longer my pound of black worms is lasting due to cheap instant mashed potatoes increasing yields.
I'm going to need at least another batch to be sure... and yet I've got plans to soon start mixing in another new food (green bean) for worms I just heard about locally.
Here are some photos - worms get no light, no heater, no love.... they are worms that get eaten... 
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CBB was never trained to use that worm feeder funnel, and worms die fast in saltwater so that funnel works much better for freshwater. Don't recommend funnel for saltwater but I may revisit this funnel later. 
Three part worm keeper is what I used in fridge. Now I use the center part as a worm strainer whenever I change worm water. Center part is useful for catching any free floating worms when I dump water. *IF* you are going to start with worms, I recommend getting worm keeper for fridge. However, if you get a LOT of worms they should not be piled on top of each other AND you can't feed worms when refrigerated so worms do get thinner over time. If you use a worm keeper and go on travel, make sure your fish sitter knows not to feed refrigerated worms as I came home to bloody smelly mess of all dead worms. About that time is when I decided I was moving out of fridge (and family was happy to no longer share fridge with live worms that sometimes looked like they wanted to escape esp if people keep leaving fridge door open to stare at human/family food)
Photo of worm tank is when nearly empty. A pound nearly covers tiny tank bottom, but there will be small patches of bare bottom. Worms love to hold onto other worms - think it is a safety in numbers evolution thing. 
SO, here is the ugly of tank worm culture - ugly degree is shipping/UPS dependent:
When worms come in from PA, I split them into 2-3 buckets each with own airstone and have learned to feed flakes (or flakes and now instant mashed potatoes too) as they seem to acclimate better from trip that way. I change water at least daily, if not hourly depending how late UPS is delivering worms (EA sends with morning delivery, UPS never meets that and depending outside temperatures, worms can arrive bloody mess from +2x longer trip than EA intended - UPS has lots of room for improvement in my area). In 2-8 days (depending how slow UPS and how hot TX) worms leave buckets and all go into tank. If its a 4-8 day transition to tank, worms may go from multiple (4-6) buckets into fewer buckets then into tank. If they arrive bloody mess, I go up to as many buckets as I can get my hands on to divide worms and ammonia production to slow the dying ones from killing healthy ones. Mentally it is bad because I feel sad for dying worms (and they smell). Financially despite this travel acclimation process, its better going this route than any other. Even worst summer arrival batch where I changed water every few hours (as my 150g RO/DI made water, after going thru my entire 55g holding tank, I used it even thru overnight hours), I saved about 50% and even with shipping being same as pound worm cost, it's cheaper than buying/restocking my worms locally. 
When worms arrive, they always seem to arrive with flukes. Fish aren't real fond of flukes, and I've found if I move worms around in buckets (or even first few days in tank), flukes will cling to plastic. I wipe them off with a paper towel and throw in trash. I pick out the ones I can when they are intermingled in middle of worms. Eventually in a few days, all flukes are cleaned out. Flukes like to die and take worms with them. I want live worms, so I don't like flukes. If fish ate flukes, I'd like flukes bit more...
Just heard about greenbeans (given whole?! seem hard for worms to eat so getting more info) so this next batch likely going to experiment even more (and not yet have concrete idea how much instant mashed potatoes are improving worm counts). Ideally, eventually if I can either start with enough to reproduce enough (but I need more space for another tiny tank ... or two more... BUT ideally want to just use my original plastic tank) 
Here is food picture. I keep instant mashed potatoes in ziplock so if I reach into bag some day and contaminate it, its not like I ruin whole box. Box is likely $1. Why I don't do this with Instant Ocean or Zoo Med flakes which cost many times more ... Don't eat green beans, so not sure what they cost, but also likely much cheaper than flake food. Keep in mind, not sure worms like flake food - I just try to make them eat flake food as it makes me feel they become better food for fish. 
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I'll cleanup this post. I'll keep experimenting. Check back over time and I'll let you know how it's going.
CBB is noticeably thicker and taller, so despite UPS causing ugly acclimation each delivery, seems like its working out okay. Eventually if I have worms reproducing fast enough, maybe I get away from UPS deliveries all together. Then it would be easy, just feed and water changes as needed (every other day ... seems less water changes having moved to instant mashed potatoes with flakes instead of only flakes)
Need instead to get canned **NO SALT** green beans, but did cut up three and feed to my worms before realizing some salt in can. Panic ran around research, but so far worms seem okay with this... but will use DIFFERENT brand going forward. BF thought worms were going into pods or somewhere else salty... my only no salt tank is my plastic live black worm culture tank.
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I haven't tried blackworms myself - but have been wanting to. reading up, it seems like no one gets them to reproduce very fast in aquariums. but there is benefit to storing and cleaning them. may still be interested in trying :)incidentally, have you looked into white worms/Walter worms? they are slightly smaller than larger blackworms but still plenty large enough to feed to adult fish. and they can be grown with self sustaining cultures in plastic shoeboxes in the dark. only drawback is they prefer cool (55-65) temperatures to really thrive (which can be a struggle here in texas). I've heard people using old fridges turned up or wine fridges, harvesting 1/2 cup worth of worms weekly from just 5-6 bins. when i get my hands on a starter again ill add a post here on them (and share if successful)incidentally, did the copper banded butterfly seem interested in the Daphnia? (i need to add a post on culturing them)
Still my copper banded butterfly shows no interest in anything except black worms. Will eat black worms once dead - they don't live that long in saltwater.
Those instant mashed potatoes made a noticeable improvement in reproduction counts for live blackworms, and I'm going more into the green bean supplemental feeding to blackworms as well. Primary food remaining instant mashed potatoes. 
We've bought some additional small tanks, and I've a theory that if I get 4lbs of live black worms reproducing, AND I'm feeding the instant mashed potatoes, this MAY be a self sustaining quantity for my fish feeding needs. If only the CBB ate live black worms, then I wouldn't need as many worms, but still every fish in the tank wants second lunch and second dinner of CBB's live black worms... 
SALT-FREE GREEN BEANS - canned and then laid out to dry a bit before being frozen. Once frozen, I bag beans then thaw beans as needed. I also chop up thawed beans to give more surface area. Primary worm food remains instant mashed potatoes (pictured above)
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My fish tank (and office) room is converted porch, so temperature isn't controlled as nicely as rest of our home. Perhaps that is why I keep failing at white worms.