from 2" - 4" in the first month for mine.
Both the Delhezi, senegal and ornate grew at least 2" and I've had them a month this weekend.
Senegals without a doubt grow the fastest. I actually have experienced the same problem in the past of slow growing bichirs. I would like to share with the others out there how I turned things around.
I kept bichirs before with african cichlids and south american cichlids and got a relatively slow growth out of them. Managed to get a 1" per month from my senegal that was in with small american cichlids. What I did this time, buy a bunch of 2" bichirs and put them in a 20 gallon long with a 30g filter attached. I feed them around 3-4 times a day they also get live minnows to hunt whenever they feel like it. I do 10% water changes every 2 days and today I did a 35%. So why i get such an amazing growth rate?
Tankmates and feeding schedule are the main reasons.
If you isolated your bichirs in a grow out and fed them well and did regular water changes they would shoot up. Bichirs are a non aggressive species and in general will totally ignore their tankmates. If they feel like they are threatened by their tankmates they will come out less and feed less. my bichirs live with a small datnoid and a Irwini catfish. they all totally ignore eachother and get along great.
stress free comfortable bichirs with suitable tankmates, good water quality and regular feedings will easily hit 1-2" per month.
Ornate day 1
2" long and extremely skinny
3 weeks later
4" fat and friednly
if you click onto my Imgur you will see that those 2 images were uploaded 3 weeks apart. good luck with growing your Bichirs!
Like to add, a well varied diet is also the key. Live, sinking pellets, shrimp pellets, cut prawns, blood worms, catfish/tilapia fillets, crickets, mealworms/superworms. try to give your bichir lots of different foods! Super worms are not an issue they do not "bite through your fish" they drown in about 10 seconds once they hit the water. If you are super worried, cut the heads off but the whole myth is a load of crap.