Need advice/help .. Blue Gill & Rock Bass nesting

I have a 75 gallon with 4 Blue Gill (from 4"-7") & 2 small Rock Bass (both about 3") which I now realize was not such a good idea. Everything was fine until my Rock Bass started building a nest a few weeks ago. He guards it violently!! He actually started building one about 6 weeks ago but I temporarily moved him since he was in the middle of the tank and defending 2/3's of the tank and giving the rest of the fish only 1/3 of it. I arranged it so if he started building again it would be at the end of the tank instead. Worked fine for a while now his aggression is getting worse and he's pretty much terrorizing the rest of the fish.

I tried to get him out of the tank which didn't work this time ... it's moderately planted and has a lot of hardscape such as a huge log, rock caves, etc. The process of trying to get him out stressed ALL the fish and pretty much scared the Rock Bass out of the nest area to the other end of the tank back to his cave. While he was gone the dominant Blue Gill decided to take over the nest and starting tail sweeping the area. Now he and the Rock Bass are fighting for it. If you've never seen a Rock Bass fight before, it's like a tornado of fish. Or imagine a dog chasing his tail only with 2 fish. The Blue Gill loses every time even though he's twice as big. Everything I read said they weren't that aggressive as Blue Gills but I beg to differ. They are actually worse than the Blue Gills since they're so quick & steathy. Like a torpedo.

The tank doesn't have a lot of open bottom area so there's no other areas for them the build nests. The Blue Gill hadn't even tried to build before this, I guess since there wasn't enough room. I could arrange it to open up more bottom space.

My questions, finally
1) If there is no open bottom space will they not try to build a nest as evident by the Gills behavior? Hopefully reducing the aggression to the point it was before the nesting started. Should I even try this .. what will the female with eggs do? I don't want to raise any fry and don't need more fish.
2) Should I remove the Rock Bass? I do have a 20 gallon I can put them in. But now the Gill is really aggressive since he got a taste of nest building.
3) Would it be better to open up the bottom so 2 nest sites are available? And/or move the 2 smaller Gills into the 20 gallon so they can have some peace and quiet. They get harassed the most now, before this they held their own? The smallest gill actually is the least afraid of the Rock Bass. I think because he can maneuver almost as good as the Rock Bass can.
4) How long do Rock Bass spawn .. especially if no females are around?

I don't have enough tanks to separate them both but can see now it's not big enough when you factor in spawning behavior. I can't afford to buy a bigger aquarium right now ... thought I'd have more time before they would need a bigger one. Although I do keep checking Craigslist there's just not a lot of them in my area and it could be months before something comes up. I don't have a pond to put them in and don't have the heart to put any down.

I got in over my head now I could really use some help and advice given my situation.

Pull rockbass. Bluegill male will spawn with female(s). If no special care given young bluegill will not survive beyond exodus (swimmup). Rockbass seem able to go through two spawning bouts in a season which likely lasts less than 30 days. Relatives such as Ozark bass and shadow bass seem to have longer breeding season. Male rockbass maybe stimulated by pheromones produced by female bluegill.

Thanks. I wondered if the pheromones from the blue gill had an effect on the rock bass. I'll try again to get them out when I do a water change to hopefully make it a bit easier. The 20 gallon I have is an odd shape .... it's unique but hopefully will work ok for the rockbass. It's already cycled and the filter would be better for rockbass than the blue gill.

Thanks. I wondered if the pheromones from the blue gill had an effect on the rock bass. I'll try again to get them out when I do a water change to hopefully make it a bit easier. The 20 gallon I have is an odd shape .... it's unique but hopefully will work ok for the rockbass. It's already cycled and the filter would be better for rockbass than the blue gill.

Probably. One trick that Corydoras catfish breeders use on tough to spawn species is to breed an easy species & use its tank water in the target species tanks to get them to spawn because of the pheromones.

Will reducing the photo period help reduce the desire for nesting in rock bass the same way it does with a longear? As long as I keep my lighting at 10 hours per day or less my longear male doesn't try nesting. I try to discourage nesting to keep him from making a mess in the tank. The tank is heavily planted and 10 hours per day seem to be enough for the plants, but it only takes a couple of days of forgetting and giving him more hours to stimulate the nesting. If it works as well with rock bass, that might be worth trying. Neither of my rock bass have decided to nest, so either photo period doesn't matter as much with them or they are both females. Whichever it is, I haven't had to discourage nesting with them. Good luck.

Edited by steve, 19 June 2012 - 03:41 PM.

Will reducing the photo period help reduce the desire for nesting in rock bass the same way it does with a longear? As long as I keep my lighting at 10 hours per day or less my longear male doesn't try nesting. I try to discourage nesting to keep him from making a mess in the tank. The tank is heavily planted and 10 hours per day seem to be enough for the plants, but it only takes a couple of days of forgetting and giving him more hours to stimulate the nesting. If it works as well with rock bass, that might be worth trying. Neither of my rock bass have decided to nest, so either photo period doesn't matter as much with them or they are both females. Whichever it is, I haven't had to discourage nesting with them. Good luck.

Yes, shorter photoperiod will suppress need to breed. Once rockbass is past his period of sensitivity to pheremones, even if female bluegill are producing breeding pheromones the rockbass will no longer respond. Darn problem we have with crappie when males and females are not properly synchronized.

Right now I have 2 lights come on about 930am until about 6pm. I have 1 light that comes on around 1pm and it stays on until about 7:30pm. Reason for funky hours is I have 4 windows that face eastward so gets some morning light although not directly on aquarium. Trying to mimic a slow buildup to "high noon". I then put the single light on to make it look like midday bright sun. Then start the gradual darkening process to simulate evening into night.

Water temps have come up a couples degrees in the last few weeks due to higher outside temps. Tank is kept in a "walkout" type basement ... meaning the ESE direction is ground level where I can walk out the back door. Water temp in the winter was below 64 (that's all my thermometer goes down to). Air temp in basement was usually between 54-62 (I assume the water temp was close to that). Air temp in basement now is almost same as tank temp which is running about 72. If it gets too much warmer I'll have to put the window a/c in. The tank is in my living room at the end of my couch .. basically it's my end table . So while I'm on the computer at the other end of the couch I do have some light on, both from the computer screen and a small table lamp. But it's pretty dim lighting. It's what I would equate to maybe a dock light or a flood light from a house located close to the lake.

I guess what I'm trying to say in a long-winded way is I think I've pretty much been mimicking nature. During the winter I only had 1 light on because I didn't have any live plants then. I shut it off shortly before dark so it wasn't on nearly as long. Added the 2-light fixture around April when I first starting adding live plants. But I've rarely had the lights on more than 10 hours.

I must have scared the rock bass pretty bad when I tried to get him out because right now he's not fighting for his nest too much. The blue gill isn't always in the nest but will keep others away from that corner, except when the rock bass ventures into it. Haven't had a chance to move him yet. I haven't noticed much tail sweeping from the blue gill, just a couple times, probably because the rock bass did a pretty good job of building the nest.

I'll probably do a water change in a day or 2, until then I'll see how it plays out and decide whether the rock bass needs to be moved. Like a said before I moved him previously but it was only 10 gallon tank. He looked so lonely and had so little swimming room although he rarely ventured out of his cave anyway. I think he knows that I was trying to move him and he remembers that experience and doesn't want to go so is trying to behave. Or maybe I'm just imagining that.

Thought I'd post an update on the situation. For some reason neither the rock bass nor the blue gill have shown anymore nesting behavior. Both have basically abandoned that spot. I had to do a 50% water change. The nitrate was getting a little high which caused a bit of brown algae/diatoms (something is out of whack, probably overfeeding trying out new foods and/or need new light bulbs). Took out some of the decorations and plants to clean them better, then vacuumed and wiped the glass good. I didn't put one of the caves back so re-arranged a few of the plants to fill in the spot. Fish seem to like it a lot better.

Not sure the reason for it but I assume I either wiped out the pheromones and/or the small change in structure has put a damper on the mood. Either way everyone is getting along better than they ever did. There's the occasional nudging going on basically saying "move .. I want that spot" but not a whole lot of chasing.

Got another question though. Right before the rock bass started building his nest I noticed him with his nose against the glass going up and down, up and down around the aquarium. He was really focused on this and nothing seemed to matter to him but that. Was he smelling pheromones? Has anyone else noticed this behavior? I found it rather fascinating to watch. Wondering if this is a sign and might be able to prevent nesting by doing a thorough cleaning when I see this happening in order to help keep the peace.