60 watts may be a little much, may not. i'm using ~30 over my 30 with ~25 gals of water in it. it's shallow though, but the lights are suspended at least a foot over the water also. i'm using cfl's so they're t3 also. this tank is heavily aerated with a very small internal pump that has a hose to deliver the water to the other end of the tank so the whole tank turns over. i would definitely put ~10" between that fixture and your tank/water to start with and adjust the height from there.
i'm also using 39 watts t5ho over my 50 and ~20 watts t8 (for the reds it brings out). basically all my plant lighting is under 1 wpg on this tank. the t8 is pretty much useless other than for color.
i've had to cut back my 50 to 10 hours but the 30 has always been on a rotating schedule thanks to it's cheapy timer. it runs anywhere from 10-15 hours depending on the day... i think ~3 15hr days and 1 10hr day a week. so cutting back the hours would be relative to the tank itself in low light, unlike high light where it's more commonly a necessity.
i believe excel is useless after a short period in the tank and that's why it needs to be added daily, unlike other ferts... so, yeah i'd definitely do daily. otherwise you may be experiencing co2 fluctuation. i do not use it so cannot comment much further than that.
for a cheaper alternative to excel you can look into gluteraldehyde. just a side note and an alternative for down the road. there's a very long discussion thread on it over on either apc or the planted tank... i think, apc. i believe planted randall may be using it too as i think he's the one that mentioned a name brand of medical gluteraldehyde recently.
sid may be on to something, actually. extra water movement would definitely make it difficult to stay settled, imo. not so sure a powerhead at the bottom of the tank would add any oxygen but it sure could move oxygen depleted water out of a stale spot in the tank.
she may be on to something else also...
when i had it the worst i was switching bulbs constantly to find what i wanted to use on that tank. it was an indecisive time when i was deciding between ge daylight cfl's and n:vision daylight cfls. basically what i found was that i could put the n:vision bulbs in there and the cyano would return (slightly), then switch back to the ge bulbs and watch it dissipate slowly. needless to say, i have switched the tank over to ge bulbs permanently unless/until i decide to upgrade to another lighting system.
adding an air stone might help keep things a bit more stable too. since you'd already be gassing off most co2 you could inject you can keep your tank at a stable level by simply utilizing the excess co2 in the atmosphere. i'd say a pump made for a 50-100 gallon tank would do just fine. since you have an hob i would think it doesn't even need to go into the tank. you can just drop an air stone in the hob most likely. it shouldn't affect your levels from your excel either... just keep it from bottoming out completely. obviously there's no risk to your stock this way either. if anything it would increase the o2 level in the tank also as well as gas off other harmful gasses. so, in general it should make for a better/healthier environment for everything in the tank.
now, like i said before i cannot safely say em/maracyn would be completely useless in your case. i will not advise against it. what i am saying is that your tank is set up for low lights and that will cause you headache regardless what you do if you don't address something (lower your light intensity or switch filters and inject co2). i am suggesting that your lighting on your tank is most likely aiding the growth of your cyano considering the rest of your parameters (including the fact you won't be able to super-saturate your water with co2 to make up for your light intensity since your hob will off gas it).
now, i have found that nitrates will play a big role... so you don't want them bottoming out. i keep mine over 10ppm to keep cyano at bay. your tank may take more with your lighting but stock in flora vs fauna i'm sure would introduce some variables so it's hard to say what level would work for you. i would definitely test that daily until you know what's going on with it/what you have to do to avoid nitrates being an issue/etc..
where i would start...
definitely take at least one bulb out
raise your fixture to ~10" above the tank somehow. it can be very ugly for now since it's temporary and you'll need to adjust the height for best performance and least/no algae/cyano. once things are fine for ~a month you can go ahead and permanently affix your fixture to a given height.
start ei dosing at ~1/2 strength and monitor nitrates boosting whenever necessary. it should not be necessary to boost your other nutrients often since nitrates are what cyano really sucks up. you should notice that when your nitrates bottom out your cyano takes off almost as if it's feeding off the plants as they struggle to fight for nutrients.
definitely dose excel everyday. a full dose may not be necessary but daily is recommended. keep in mind i don't use it so others may disagree, but i doubt it.
shade your lower light plants with other plants/floaters. the lower demanding plants are definitely more susceptible to outbreaks and if you have any plants that break the surface they can utilize co2 from air to keep algae/cyano from getting a strong foothold.
address any dead spots in circulation within your tank. nutrients/oxygen/co2/etc. will not be delivered to these areas as well to feed your plants giving cyano the advantage it needs. an air stone or pump should be sufficient for this matter.
once that is all taken care of and you are certain everything seems fine you can try other things if necessary.
if you are using the maracyn and it seems to be working i wouldn't stop now. BUT, i would definitely address your light vs carbon situation by whatever means necessary. the most economical way to do it is to reduce your light intensity. like i said... since you're not injecting co2 DO NOT BE AFRAID to add aeration... it cannot hurt at that point!
good luck... you'll get it.
