Long term colony care

[Matttoadman]

So I have had a colony of Eublaberus serranus since 2016. I have kept them in a 10 gallon fish tank with around 6 inches of coconut fiber , bark pieces and stick for the adults to rest on. I usually see around 30 adults with several dozen nymphs of various sizes. I keep the substrate mostly damp and mist weekly, feed oats a couple times a week, and add fruit and veggie scraps almost daily. I feed cat food sporadically. The temp is 75-80. The numbers are with me removing some for feeding my lizards. But that was usually 12-24 nymphs a week and maybe 2 males a week. But my numbers held. The past several months my numbers have dropped. I have maybe had 6-12 adults and a couple dozen almost ready to mature and a couple dozen fresh nymphs. I stopped pulling out any to feed. When I add food it used to disappear with in seconds. Now I see oats and fruit on the surface for days. I have had to remove it to keep out flies. No dead found. Do colonies start to fizzle over time? Do I need to add some fresh blood? The substrate looks the same as always(smells like fresh garden soil) but maybe I need to refresh the substrate or add to it? Any other tips for maintaining a colony long term?

[Allpet Roaches]

Try moving some or all to a new setup. My serranus is from maybe 2007 and they seem fine in the same cage. I have other roach colonies that have been in the same cage since 1995. My discoidalis I've had since 89 and the portentosa are an unmixed line from 72. Usually a change in care level, or differences in weather that affect indoor conditions are the problem. There is afungus that can wipe out a colony but I've only seen the fungus take out Corydia and Polyphaga and it still takes a few years to blow out a decent colony. Sadly it ends in 100% mortality eventually no matter what you do. 

[Matttoadman]

I haven’t seen any evidence of premature death so hopefully it’s not that. I did a partial substrate change (1/3) cause I realized it has been a while since I added any.  I also moisturized all the substrate and removed any debris. I found a lot of peach and cherry pits, pumpkin stems etc. my wife reminded me we were feeding three leopard geckos and a bearded dragon and added three more leopard geckos. So have a feeling I have been feeding from it more than I realize. I looked through it last night and I found several newly matured adults. I also got a start of Eublaberus “ivory” to get a second colony going.