changing balances - more plants = less algae = aggressive SAEs?

[helenf]

I only have one tank (plus a quarantine tank) these days, and it's been giving me trouble.  But I have a theory (yeah, run now), and wanted to run it past anyone who cares to read.

My tank is a heavily planted 220l tank (that's about 55 gallons) with goldfish, SAEs, corys and a few too many guppies in it.  It runs at about 24 degrees (heated by the T5 lights, the heaters never run except in the depths of winter - I only have heaters at all to make sure that the temp stays stable the year around).  It's been running for a year now and I've been very happy with it because with it I achieved my aim of getting fast enough plant growth that the goldfish didn't destroy the plants (in a low-tech way, 2 39W T5s and intermittent additions of biological carbon and ferts, but no CO2, no EI, nothing that takes that much time).

The first thing that I noticed happening was that one of my goldfish got sick and died.  About a month ago now.  I'm not so worried about that because none of the others seem sick and I think maybe it was just one of those things that happens to petshop fancy goldfish.  What I mean is that I think that wasn't my doing, but something that was just going to happen. 

Anyway, the next thing I noticed was that the SAEs, or at least one of them, is nipping the tails of the other goldfish.  There are 5 SAEs in there, normally they chase each other but ignore the other fish.  They spend a lot of time grazing, and lot of time sitting on leaves or wood, and are not, in general, particularly active and certainly not aggressive. 

The other thing that I notice at the moment is that the plants are looking great.  There is masses of hygro-somthing (I think it's a plant I bought as "green temple", a larger-leaved hygro variety).  Normally I have a lot of it around but it all looks shabby, as the goldfish eat it.  But all over the tank it's growing very fast and not eaten at all.

Now, the thing I am wondering is whether this makes sense: what is the goldfish that died was doing most of the uprooting and chewing of plants.  What if now the plants are able to grow faster and be less destroyed means that there is less of some type of algae.  What if that means that the SAEs are hungrier and developing a taste for goldfish fins?

I have not really noticed there being less algae, mind you.    There is algae all over the back of the tank and fairly heavy layers on some of the older anubias leaves etc.  But maybe there is less of some particular kind of algae that the SAEs like, I dunno?

Do you think this is even plausible?

I attempted to catch out the offending SAE but I can't catch him.  Firstly it's hard to be sure which one it is once they start swimming around, and secondly I'm just not fast enough.  I'd have to remove all the plants and wood and the other fish before I'd have a hope of catching these guys. 

So now I'm trying another tack: overfeeding.  I've doubled the amount of food I'm adding to the tank, feeding several times a day, and I plan to keep this up for a few days.  While I think this won't do my NitrAte levels any good, I don't expect it'll effect ammonia/NitrIte at all because the plants will suck up the extra ammonia and the tank is very mature with a decent filter.  I don't want to overfeed for a long time, but I'm wondering whether it will, for a short time, satisfy the SAE's hunger and mean that they are less enthused about bothering to chase the goldfish.   Not sure if it's working yet - I haven't had time to watch the tank much today. 

Do you think this makes any kind of sense?  Any other ideas? 

Do you know what I mean when you just get this sense that something that was previously balanced in a tank is now unbalanced in some way, so adjustments are necessary.  I still need more experience at figuring out these things...

(thanks for reading what turned out to be a rather long post)

[Essabee]

Watchout everyone - Helen is back with a bang.           

Changing balances is right - bigger SAE in relation to your gold fish size. Older larger SAE with need for greater space. Sexually matured SAE with need for more nutritious food than algae for spawning readiness.

There is a easy way to cater to this need. You have already taken one step - more food; now take another - give the aquarium a good trimming. That will increase the swimming space. Take another step - scrub of the old algae on the rear wall, the flora is populated predominantly with those algae that the SAE find inedible. You will open out the space for greater variety in the algae flora.

Aggressiveness comes with maturity, you cannot help that but the steps I advised will go to dissipate some of that.

The other way is to trade off the matured SAE for younger ones.

[helenf]

Essabee all those ideas seem like great ones, thanks!    I was thinking of trimming the plants back quite a lot (much as it pains me to throw out perfectly good plant growth).  But the idea of scrubbing the back wall is a really good one and I wouldn't have thought of that.

I don't think I can catch the SAEs to trade them, at least I haven't managed to catch the one I've been after.  Interestingly it's one of the smaller ones in the tank, not the largest, that is being aggressive.   The fish in question is maybe 3 or 3.5 inches long, about an inch shorter than the largest of them. 

[wendyjo]

I use 2 large nets to catch SAE's - I use one net to herd the fish into the other net.